Overview
Stricter international regulation enacted in the early 1990s and advances made in the design and safe operation of tankers saw a significant improvement in safety record of the tanker industry. According to the International Tanker Owners Pollution Federation, oil pollution from tankers for the period 1997-2003 was only 25% of the pollution for the period 1990-1996. The total number of reported tanker incidents with pollution for the period 1997-2003 was only 37% of the figure for the period 1990-1996, while at the same time the total oil trade had increased by 15%. Two particular accidents, though, detracted from the tanker industry's good record. The cause and effect of the Erika (1999) and Prestige (2002) incidents, with their heavy oil cargoes causing extensive pollution on European shores, have had major political, social and economic implications.
Single hull tankers are gradually being phased out, according to the International Maritime Organisation's global regime, but in 2005 Europe went beyond international regulations and implemented a unilateral accelerated phase-out, which has since led to the international phase-out being accelerated too. The control system for tankers has also been tightened up at the same time as the industry itself has taken initiatives to ensure that the structural integrity of tankers is maintained to good standards throughout the life of the ships.
Despite the political and economic importance of these issues, some of the relevant regulation still tended to be made before incidents were properly investigated. Political pressure rather than proper risk analysis may determine which types of oil tanker pose the highest pollution risk, the relative safety of new tanker designs, or the most appropriate response to an evolving oil pollution incident. To address this issue rationally, the European Commission commissioned the POP&C research project.
The POP&C project aimed to deliver a framework and suitable tools for a methodological assessment of risk. This was undertaken to provide a rational basis for making decisions pertaining to the design, operation and regulation of oil tankers. Such support can be used to make more informed decisions, which will in turn contribute to reducing the likelihood and severity of future oil spills.
The specific objectives included developing:
- a risk-based methodology to measure the oil spill potential of tankers;
- a risk-based passive pollution prevention methodology (design and operational lines of defence);
- a risk-based, active, post-accident pollution mitigation and control framework.
The main project steps were as follows:
- Identification and ranking of critical hazards such as collision and grounding, fire and explosion and structural failure;
- This leads to estimates of probability of capsizing/sinking from loss of stability or structural failure;
- Combined with estimates of consequences within a risk-based framework, the above will provide a pollution risk;
- Development of risk reduction through preventative measures;
- Development of post-accident mitigation and control measures such as decision-support tools, the human-machine interface and safe refuge.
Deliverables included pollution risk methodology and assessment tools, decision-support tools for pollution prevention and crisis management, and design and operational guidelines for containment of pollution risk.
Funding
Results
1. Hazard Identification and Raking
The first step of a risk assessment methodology was to carry out a Hazard Identification and Ranking (HAZID) study.
In order to demonstrate the methodology developed, the POP&C project decided to analyse the AFRAMAX class of tankers because of the relatively large market segment of the AFRAMAX tankers, past spectacular catastrophic tanker accidents involving AFRAMAX tankers and relatively high number of single hull AFRAMAX tankers which are currently operational and expected to continue operating until they reach the recently amended (accelerated) phase-out date.
Several mainstream techniques (What-If Analysis, What-If/Checklist Analysis, Hazard and Operability Analysis, Failure Modes and Effects Analysis, Fault Tree Analysis, Event Tree Analysis and Human hazard Identification) were used for hazard identification and ranking in the maritime world. These methods were reviewed and a method utilising Fault Tree (FT) and Event Tree (ET) techniques was selected to be used in the project.
A ranking methodology was developed according to the project objectives; three classifications of risk were proposed, addressing the three types of consequences that should be considered in the project, i.e. human safety, property and environmental impact.
On the basis of the incidents highlighted previously and the fault trees and event trees that were developed, a generic risk model for tankers was built. The POP&C risk model consists of six bow ties, one for each category of incident. Pollution is considered as a potential consequence of the incidents; as such it is embedded in the sequence of events following the occurrence of the incident. Because it is impossible to produce a universal risk model covering all aspects relative for safety, it was decided to perform a more general screening of all the possible accident scenarios that can lead to a vessel’s loss of watertight integrity. Based on this screening, specific areas of concern, where risk has to be reduced, were identified by ranking different scenarios according to their risk level.
The second objective was to identify the most critical accident scenarios. Each scenario is characterised by three risk indexes, one for each type of consequence: human life, property and environment.
The ranking process was split in two steps, the event tree analysis and the fault tree analysis. The outcomes of the risk analysis have been very positive. The most critical acciden
Technical Implications
Following the Erika and Prestige incidents, IMO adopted revised phase-out schedules for single hull tankers, which set out a stricter timetable for the phasing-out of single-hull tankers. Also, a specially enhanced inspection programme (ESP) has been introduced to ensure better through-life management of tankers.
Despite the political, social and economic importance of these issues, some of the relevant new regulation still tends to be made before incidents have been properly investigated.
Through the findings of the POP&C project, authorities, regulators, designers and operators can make (undertaking a methodological assessment of risk) rational decisions pertaining to the design, operation and regulation of oil tankers.
The POP&C project contributed to the European Union's scientific and technological objective of 'Increasing road, rail and waterborne safety and avoiding traffic congestion' through the risk-based pollution prevention and control options that:
- provided a framework to assess the oil spill potential of both existing tankers and new designs in a rational way;
- integrated existing and developing technologies to provide operational assistance so as to improve the safety of tankers;
- assessed the effectiveness of computer-based decision-support tools and information services on the condition of vessel operational responsiveness, to yield risk reduction through prevention and mitigation;
- encouraged best practice in the tanker shipping community.
Foremost among these contributions, POP&C could assist in reducing the number and severity of oil pollution incidents by providing a more rational basis for designing, operating, and regulating oil tankers. Reducing oil pollution at sea is an important step towards achieving environmental and economic sustainability for future transportation systems.