Tanker spill risk in the Gulf of Finland: dire consequences, high uncertainty

In the Gulf of Finland there are 6000 -7000 tanker calls every year. Of these around 1000 call at Finnish harbors. These tankers carry everything from crude oil to petroleum products to chemicals, with around a third of the tankers calling into Finnish harbors carrying chemicals. While the oil tanker spill risk is common knowledge, the risk posed by chemical tankers has been largely been ignored in the public discourse.

Luckily so far no tanker accident has led to a catastrophic environmental disaster due to a spill of oil or chemicals, but unfortunately this seems to be only a matter of time: The average period between tanker groundings is once roughly every 2 years according to statistics for the Finnish GoF only.

Tanker spills are potentially high consequence, low occurrence but high uncertainty events. The uncertainty here refers both to the high variance of historical accidents in the Gulf of Finland as well as the lack of understanding in the scientific community in modelling accident frequency and consequences.

There are several key issues when it comes to analyzing maritime risk: Accident underreporting is a serious issue – even in the Nordic countries. Roughly half of all accidents are estimated to go unreported (or alternatively be lost somewhere in the system). Thus any analysis based on accident statistics is incomplete. To which extent this affects only minor damages is uncertain.

When it comes to groundings, there are several methods available for estimating grounding damage. These, however suffer from the fact that the actual bottom shape is not very well known; only little research has been done so far and the rock models used in litera¬ture are too simplified to realistically correspond to actual sea bottom shapes, which is one of the most critical inputs required for grounding damage modelling.

For collisions ship bows are known to a higher level of detail but the exact “how often” and “where” are not as there are major simplifications being made the ship collision modelling: Utilizing different assumptions regarding how ships behave in the moments up to collision lead to different accident patterns and frequencies in the Gulf of Finland. These factors – just to name a few – mean that there is medium-to-high uncertainty of the risk estimates.

Despite this, uncertainty of maritime risk is rarely discussed in the scientific literature. This can lead to problems higher up in the decision-making chain: Researchers presenting numbers backed up by fancy-looking mathematical equations and references to scientific publications easily create an illusion of accuracy and reliability to peo¬ple higher up in the decision-making chain. This leads to a false sense of trust in the numbers, which themselves in maritime risk analysis are usually subject to medium-to-high uncertainty.

When you are presented with numbers regarding how often accidents are predicted to happen and what the spill sizes are, you should ask critical questions such as “how realistic are these numbers?”, “how reasonable are the assumptions and simplifications made in the modelling process?” and most importantly “how do the aforementioned affect the results?”.
As tanker accidents are high impact-high uncertainty events, risk mitigation measures should be more designed around a robust response thinking instead of being designed around expected values such as ones derived from a cost-benefit analysis as the expected accident frequencies and consequences are highly uncertain. Conducting a comprehensive cost-benefit analysis is also practically very difficult to do as exploring the effects of all potential risk mitigating measures is practically challenging or impossible.

Robust in this sense means having the capability of respond¬ing effectively to a wide range of spills in the Gulf of Finland utilizing various collection and containment methods. Such an approach is to some extent adopted in the HELCOM recommendations, where member states are obliged to certain oil spill recovery capacity and speed standards. The collection of spilled oils is much more expensive on the shores than at open sea, which should of course be kept in mind when planning the response capacity.

Preventive measures should, however, not be forgotten but authorities should have the attitude of “when, where and how much” instead of “if ever” when it comes to a major tanker spill in the Gulf of Finland.

Otto Sormunen and Pentti Kujala
Aalto University, School of Engineering
Research Group on Maritime Risk and Safety

Expert article published in Baltic Rim Economies on 31.10.2016