More than a year after the Costa Concordia cruise liner ran aground and capsized off the coast of Tuscany, salvagers have righted the cruise ship during a complex, 600 million euro ($800 million USD) engineering project and will tow the vessel from Giglio Island on which it rested. But before that could happen, the plan required installation of a stabilization and holdback system, completed by Trevi Group of Italy.
The 300-metre long, 114,000-ton cruise ship hit the rocky reef and wrecked on January 13, 2012, claiming 32 lives. Costa Crociere, the ship’s owner, hired Smit Salvage BV of The Netherlands in collaboration with Tito Neri srl of Italy to remove 2,042.5 cubic metres of fuel and 240 cubic metres of sewage from the ship, while authorities considered plans to salvage the vessel.
Titan-Micoperi, a partnership of Crowley Group’s Titan Salvage, a marine salvage and wreck-removal company, and marine contractor Micoperi of Italy proposed a six-phase plan to remove the ship for offsite salvaging while protecting the ecologically sensitive coast. Costa Crociere and the Costa Concordia Emergency Commissioner’s Office hired Titan-Micoperi in April 2012 to perform the ship recovery.
The six-phase plan included the installation of a stabilization and holdback system to prevent the ship from slipping or sinking further; preparation of an artificial seabed for the wreck to rest on after it was righted; installation of 15 refloating sponsons on the port (exposed) side of the wreck; parbuckling, a 65-degree rotation of the ship using strand jacks; and attachment of 15 refloating sponsons to the previously submerged starboard side of the ship. The ship would then be towed to a shipyard and dismantled.
The sheer size of the cruise liner, its position relative to the shore, and the risks related to its removal made the salvage the most complex ever attempted. About 500 people from 26 countries – engineers, divers, welders, technicians and more – have been working 24 hours a day, seven days a week on the project, stopping only for rough weather conditions.
Several crucial preparatory activities were needed before any salvage operations could begin, including a seabed investigation to determine the geologic conditions of the site and the installation of an anchor system to secure the wreck before winter storms could further damage the ship.
The Trevi Group, a foundation engineering and construction company based in Cesena, Italy, joined the Titan-Micoperi team in June 2012 to perform this work.
RCT Srl, a Trevi Group division that specializes in geotechnical and geologic investigations, performed the subsurface mapping using a Soilmec SM-20 microdrilling rig for the survey. Soilmec is a company within the Trevi Group that specializes in the design and production of machinery for special foundation works. The SM-20 is a multi-purpose hydraulic drill rig with a weight of 20 to 22 metric tons that was operated from a barge adjacent to the ship’s hull.
Giglio Island, located about 20 kilometres from the western coast of Italy in the Mediterranean Sea, is comprised primarily of granitic rock. RCT found both solid and fractured granite at the shipwreck site. The fractures are generally filled with loose, running sand and gravel that presented additional challenges to investigation and construction.
Anchor Construction for Ship Stabilization
A sophisticated hold-back system was crucial in stabilizing the ship and preventing slipping to deeper water. Titan Micoperi installed four large seabed anchor blocks, weighing more than 30 tons each, between the center of shipwreck and the shore. Trevi used a Soilmec SM-21 to install ten tendons into each of the four anchor blocks to secure the blocks to the seabed by increasing the friction between the anchor block and the rock below. Installing the tendons was complicated by the underlying rock fractures.
The SM-21 was mounted with a Wassara down-the-hole hammer drill secure the anchors. The water-powered percussive drilling technique offered environmental benefits, as it doesn’t require oil for lubrication of the hammer, thereby reducing pollution risk. Using high-pressure compressed air to power the hammer was not permitted.
In order to monitor the load applied to the anchor block, a load cell was installed on each anchor block and connected to a data logger to allow real-time transmission of data.
During drilling, drill cuttings were brought to the surface and managed and treated on the barge using flocculants and a coagulant to separate the solids from the seawater for more effective disposal. During drilling, Titan-Micoperi monitored the seabed using a remotely operated vehicle (ROV) to ensure that the sensitive marine environment was not adversely impacted.
Trevi completed this anchor construction work in late October 2012. Metal structures weighting over 30 tonnes each were secured to the anchor blocks. Steel chains were then connected to the anchor blocks, threaded under the ship’s hull, and attached to portholes on the port (exposed) side of the ship for stabilization. This holdback system prevented the ship from slipping further into the water and was also used during ship parbuckling.
Seven additional anchor blocks and associated tendons and load cells were installed during the parbuckling operation, upon which special towers and hydraulic jacks were assembled.
Cables connected to all of the anchor blocks were individually controlled by a strand-jack system to help support the ship’s mid-section. Trevi completed this portion of the project in July 2013.
On September 17, 2013, after 19 working hours, Titan-Micoperi righted the ship and began the next phases of salvage.
Tiberio Minotti was Trevi’s project manager for the Costa Concordia project. Vincent Jue is a Vice President with Soilmec North America. Soilmec manufactures drilling and ground engineering construction equipment. Reach Vincent at firstname.lastname@example.org.