With one of the worst marine disasters followed the need for the wreck of the MV X-Press Pearl’s removal in a manner that would not result in further damage to the already immensly affected environment.
Chartered Engineer attached to the Department of Coast Conservation and Coastal Resource Mangement, D.T. Rupasinghe said the removal of distressed ships from the sea is a complex scientific process involving the use of modern technology.
The MV X-Press Pearl vessel entered Sri Lankan waters on 19 May 2019 and a fire broke out in the vessel on 20 May following a nitric acid leak that rapidly spread across the containers in the ship and its bridge.
Due to the intensity of the spread of fire due to strong wind, the inferno could not be contained and on 2 June, the ship sank 21 metres deep together with hazardous and noxious substances impacting the water, air, land, estuaries, sediments, food networks on a short term.
Rupasinghe said in the long run, the effects of Hazardous and Noxious Substances (HNS) and micro-plastic in the marine environment could devastate the food network as well as the biodiversity.
He added that among the substances contained in the vessel that may or not be added to the environment are 348 MT of bunkering oil, nitric acid, caustic soda, methanol, and other hazardous chemicals contained in 81 containers, 87 containers with micro-plastic and other plastic while the total number of containers in the vessel were 1,670 which were either completely or partially burnt while there are 1,086 containers in the cargo hold.
Wreck and debris removal
The ship and ship debris removal process has been divided into two phases, while the initial phase involves the removal of the debris of the ship underwater (from the containers to the ship’s hull), the second phase involves removal of the shipwreck, he noted.
Accordingly, a survey of Multi Beam and Side Scan Sonar on the seabed by Remotely Operated Underwater Vehicle (ROV) has identified 300 sites where debris of the vessel has spread.
The consulting company, the insurance company and the P&I Club representing the vessel owners chose the Resolve Marine Company of USA for the removal of debris spread underwater and they have completed the said task, Rupasinghe explained.
The Shanghai Salvage Company was selected for the removal of the shipwreck and they had developed two strategies. One is to split the ship into two at the crack that had appeared in the middle of the ship hull, Rupasinghe said citing the information provided by the company.
The second strategy is to remove the ship in its entirety if the crack does not affect the ability of removing it in such state and the Tandem Lifting mechanism will be adopted for both strategies.
However following the survey carried out through ROV and divers, it was observed that due to the crack in the ship hull, the ship could be unstable if lifted in its entirety and thereby they decided to spilt the vessel into two before its removal. Thereby as the first step, the ship’s control and bridge was cut off to reduce its weight.
While two floating barges with cranes have been stationed on either side of the ship, one has been named as ‘Cali’.
Cali with the use of a Horizontal direction drilling machine, sends a pipe through the seabed beneath the sunken vessel to the other floating barges with cranes and the latter connects a cable to the pipe.
The Cali vessel then tugs the pipe back and places the cable across the sunken vessel. Accordingly, 63 cable wires covering the whole ship will be placed, out of which, 28 will be at the rear and the remaining 35 to the front.
The vessel is then split into two between the two cargo holds where the containers are stored. Accordingly, the front section is 105 metres in length and 18,000 tons in weight while the behind section is 81 metres in length and 13,000 tons in weight.
The splitting will take place with the use of a friction chain and the cutting will be done by pulling the friction chain back and forth in the same manner that the cables are sent to lift the vessel.
After the vessel is cut, two tandem lifting cranes are stationed and the 35 cables attached to the front of the vessel are brought with the help of divers with the use of a floating crane and the two ends of the cables will be attached to the strand jack of the tandem lifting crane and when the tide is out, the cables are slowly pulled together.
When the cables are so lifted by the strand jack, the water in the cargo hold is pumped out and the weight of the ship is further reduced.
After the vessel is lifted to the required amount, it will be placed on a semi-submersible ship which is a specially designed vessel used to transport large ships or other heavy parts by sea.
Once the cables are removed from the part of the ship, it will be transported to the designated area by the Semi-Submersible Ship and would most likely transported to the Ship Breaking Yard in Pakistan or Bangladesh, Rupasinghe said.
On 6 April 2014, a passenger ship Sewol-Ho sank in South Korea killing over 300 University students and three years later, the Shanghai Salvage Company used the same mechanism and with the use of 99 cables, to remove the shipwreck, he said.
Currently, owing to the southwest monsoon, all 63 cables have been connected to the vessel and has been located on the seabed and the process has been temporarily terminated. Thereby the Floating Barge has been temporarily removed from where they were stationed and the removal will commence after the monsoon in October 2022, Rupasinghe said.
Marine Environment Protection Authority (MEPA) said the removal of debris and the wreck continues under their full supervision. MEPA officers are on duty 24 hours a day to monitor the situation. They provide advice on minimising marine pollution and also takes necessary steps to obtain samples for relevant tests while noting that about 78 per cent of the waste has been removed.
“The waste removed from the ship is collected in containers and transported to Wattala container yard which operates under the supervision of the Marine Environment Protection Authority for safe storage,” MEPA noted.
By Faadhila Thassim