This study will create a precedent

Rene Arikas. Photo: Sander Ilvest

Minister of Finance Keit Pentus-Rosimannus signed a decree on Monday allocating 1.6 million euros from the government reserve fund to the Safety Investigation Bureau (OJK) for underwater investigation of the wreck of the passenger ferry Estonia.

The government made a principal decision to allocate a total of three million euros for the study of the wreck at a cabinet session in March and Sweden will contribute a similar amount. The first party of Estonia’s contribution allocated this week will be used for concluding contracts and arranging tenders; the remaining sum would be used next year.

Rene Arikas, head of OJK and of the investigation, said that the present task of the center comprises initial assessment and determining whether the conclusions provided in the final report of the joint accident investigation commission (JAIC) of the loss of the Estonia are still valid. The leading state of the new investigation is Estonia; the commission members come from Estonia, Sweden and Finland.

“The official designation of the activity is initial assessment. The investigation has to determine the causes of the existing and previously unknown breaches of the hull.” Arikas described the purpose of the study. The commission’s work would be concentrate solely on the hull damage and what might have caused it; checking on other versions and theories is not a part of its tasks.

Preliminary studies to be carried out this summer

Arikas said that the upcoming work would be the first such project ever. No other wreck in such a depth has not undergone that detailed digital models, their analyses and simulations.

“This study will create a precedent. The technology is the most up-to-date available. The digital model to be created will comprise a detailed 3D image of the ship, the bow visor and other details; the model will also cover an area of 300 – 500 meters around the wreck where debris could have fallen, as well as part of the seabed which could have affected the hull,” the OJK head said. The digital models would be used to carry out various simulations which take into account all known circumstances and are to determine the cause of the hull damage.

“We shall carry out laser scanning of the bow visor and determine what kind of damage and how it sustained, as well as the shape of the physical object which could have caused the damage,” Arikas described the use of the simulations.

Preliminary research covering undersea currents, their direction and speed, the transparency of water and its oxygen content , as well as scanning the wreck and its vicinity with sonars, would be carried out in the Ristna-Utö-Hanko triangle on July 8 –18. Arikas assured that the Finnish and Swedish law amendments permitting underwater operations in the burial site area would have come in force by that time.

“The seabed geography, currents, relief and visibility under water have not yet been studied in that area. Currents have different directions in different layers of water and have the speed of up to one meter per second. We shall use a research vessel of the University of Stockholm, the Electra, built in Saaremaa in the Baltic Workboats plant. The mothership of the investigation will be the Transport Administration’s multipurpose EVA 316 granted to us as an inter-departmental aid,” Arikas said. The sensors measuring the speed and direction of the currents, the transparency and oxygen content of water would be set up on the bottom while autonomous sensors would be moving around independently.

A sideview sonar would be used to create a three-dimensional image of the ship’s hull and the seabed, while a multibeam fan sonar would provide detailed information about depth.

“We shall use different technologies, both hull-mounted and towed sonars. Technology does not limit us; we can place an autonomous robot on the seabed. But the initial plan calls for the use of a ROV or a remotely operated underwater sonar,” Arikas explained.

The preliminary studies will be used to create a three-dimensional image of the bottom which will be complemented with hydro-geological information about the composition of the seabed, e.g. where are clay, sediments or fossils. Proceeding from that image a magnetic study of the seabed will be carried out next to find all metal objects on the bottom and determine their shape and weight, including both objects related to the shipwreck and possible remnants of the war in order to make sure there is nothing posing explosion hazard. The preliminary study reports have to be completed by September.

There will be no manned dives

The bathymetric or sea depth study will be carried out in February-March 2022 when the water transparency will be at its top and the regular powerful storms will be over. Acoustic 3D scanning will be used to crate a detailed 3D image complemented by photo-geometric image during the main part of the study, which will provide detailed information about the damage and the surrounding hull down to the thickness of the corrosion layer.

“If necessary, samples of the soil will be taken to help with conclusions about the seabed below the hull. The submarine filming made for the TV channel caused fresh damage, for example, “Arikas said.

According to current information, no manned diving is planned.

During the main part of the investigation, the arm of the remotely operated vehicle would enter the ship’s hull, but only in order to study the possible damage to the internal structure around the openings and the extend of damage. After the digital simulations have been completed, they will be compared with the facts established by the investigation. Making conclusions would take place between April and July while the final report would be completed by August 2022.