Method Development for Environmental Risk Assessment of Shipwrecks
Potentially polluting shipwrecks containing oil or other hazardous substances may pose
a threat to the marine environment. This is a global problem and many shipwrecks stem
from the Second World War and have been deteriorating on the sea floor since then.
Only in Swedish waters there are more than 2,700 wrecks that warrant further
investigation and 31 of these are given a very high priority due to the environmental
threat they pose. These wrecks are together estimated to contain between 1,000 and
15,000 tonnes of bunker oil. Every shipwreck poses a unique threat depending on, for
example, the type of vessel, cause of sinking and environmental preconditions.
Currently, there is no comprehensive method for assessing the environmental risk
posed by shipwrecks and providing necessary support to decision-makers.
It is not feasible to remediate all shipwrecks due to costs but a proactive
approach would make it possible to avoid the need and high cost of reactive response in
case of an oil leakage. In order to effectively use resources, proper decision support is
needed. Risk assessments and the overall process of risk management are important
means to provide such decision support. The purpose of this thesis has therefore been to
develop a framework for risk management of potentially polluting shipwrecks and a tool
for quantification of the probability of release of hazardous substances from such
shipwrecks. This was achieved through a comparison of current methods for risk
assessment of shipwrecks in order to identify development needs. Based on the
comparison, a generic framework for risk management of shipwrecks was suggested.
Furthermore, the tool for estimating release probabilities was developed based on a
probabilistic fault tree approach with the aim to support the risk assessment part of risk
management. The tool makes it possible to consider possible events that may damage
the wreck as well as physical and environmental conditions affecting the wreck.
The results from the comparison of current methods for risk assessment of
shipwrecks showed that none presented a holistic risk assessment guide and that there
is a lack of quantitative risk assessment tools for shipwrecks. Few methods considered
uncertainties and the need of sensitivity analysis.
The generic framework for risk management of shipwrecks clearly shows the
important steps that need to be performed and how they are linked. It also emphasizes
the need of proper assessments to facilitate an efficient resource allocation for these
types of environmental threats. The tool for probabilistic risk assessment of shipwrecks
enables uncertainty analysis and is a first step towards a holistic risk assessment
environmental risk assessment
fault tree analysis