Downers and leaners

Lack of escape routes Persons on board Cyclones/hurricanes Downers and leaners Blowouts Hydrogen sulfide Dropped objects Helicopters Ship collision. 

Even when the water is shallow, it is not safe to send divers into a downers and leaners situation because the unstable structure may collapse while the divers are in the water. Moreover, if the wellhead has not been properly decommissioned, a gas blowout could occur at any time—once more posing a great risk... 

One of the responsibilities of the U.S. Coast Guard is to ensure that any collapsed, or partially collapsed, platforms are removed so as not to present a hazard to shipping. This is a particular concern following a hurricane when some of the older, inshore platforms may be knocked over by the winds and high seas. Such platforms are sometimes referred to as downers and leaners. ... 

These damaged platforms have to be removed because they pose a hazard to shipping. However, their removal is time-consuming and expensive. One operator had a cluster of about a dozen downers and leaners, all in the same general area and about 150 ft of water. The cost of removing the damaged structures was over US1 billion. The wells associated with the platforms were producing very little oil and gas so it was... 

Even when the water is shallow, it is not safe to send divers into a downers and leaners situation because the unstable structure may collapse while the diver is in the water. Moreover, if the wellhead has not been properly decommissioned, a gas blowout could occur at any time—once more posing a great risk to divers in the vicinity. This means that Remotely Operated Vehicles (ROVs) have to be used. Explosives are rarely used because of the potential impact on turdes and other marine creatures. Chemicals, including diesel fuel, that were on board the facility at the time of the platform collapse, pose an environmental hazard and can be a safety hazard for divers in the area. 

When a platform is destroyed during a hurricane, it usually remains in place—in a severely damaged condition. If it sinks and rests on the seabed then it is a downer. If it partially collapses, with some structure showing above the sea surface, then it is a leaner. ... 

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