On June 3, 2002 the 5,970 dwt, 104m x 20.5m x 4.9m “Clipper Cheyenne”, sunk alongside the dock at Foynes, Ireland in the pristine waters of the River Shannon
, while ballasting to load a floating dredger.
The vessel sank in a position alongside and parallel to the quay with the bow of the vessel to seaward, a list to starboard and laid in approximately 11 meters of water at low tide. The tidal range was about 4 meters on spring tides with virtually zero visibility and conditions outside of the hull were further exacerbated by a strong river current. The “Clipper Cheyenne” had 244 tones IFO 180, 36 tones diesel oil, and 11,000 liters lube oil onboard.
Immediately upon being notified of the incident, a Titan Salvage Master and Salvage Engineer were dispatched to the scene via a chartered aircraft from Titan’s UK Salvage Depot. Soon after arrival Titan was awarded a contract to plug vents to control the escape of hydrocarbons from the vessel.
Titan was awarded the re-floating contract on a Lloyd’s Open Form on June 5, 2002. Titan quickly began mobilization of equipment & people from their New Haven, UK and Ft. Lauderdale, Florida warehouses. A total of 19 Titan personnel, including Naval Architect, and Diver/salvors were sent to the site.
During discussions with the local Harbor Master
and Coast Guard, it was decided that the risk of pollution was greater if an attempt to remove the hydrocarbons prior to re-float was undertaken. Therefore it was decided to completely contain the hydrocarbons within the vessel.
Various refloating scenarios were evaluated using detailed computer models. The models showed that without any external support the vessel had very little, if any, stability when she left bottom. This lack of stability was the principal challenge for re-floating the vessel. To provide this support it was decided to first roll the vessel to port and then let her lay against the pier during the re-float. A barge was then attached to the stern of the vessel to provide additional waterplane area during the most critical phases. As an additional effort to improve the stability situation, the crane booms of the CLIPPER CHEYENNE were lowered and removed, thus decreasing the overall center of gravity for the vessel.
For the refloat, the vents on the wing tanks were blanked and fitted with blow down fittings and modified vents. To prevent the air from escaping from the ballast tanks, all the valves for the ballast system had to be closed by divers. Pumps were then fitted in the accommodation and foscle areas to give buoyancy up forward and increase the ground reaction aft.
The starboard wing tanks were blown down which caused the vessel to roll to port and come to rest against the pier as planned. After further prep, the watertight door to the pump room was opened and the remaining wing tanks were blown down in a calculated and controlled order, bringing the vessel to the surface on Sunday July 7, 2002.