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Marine Log

March 14, 2007

GAO says LNG tanker terror attack consequences need more study

The GAO has issued a report saying that the "public safety consequences" of a terrorist attack on an LNG tanker "need clarification."

The report was released yesterday by the House Committee on Energy and Commerce, which is planning to hold hearings.

The report has already been seized on by opponents of LNG terminals and generated one Massachusetts headline proclaiming: "Reports say terror attack could burn people one mile away."

What does the report, in fact, say? You can download it here, meantime here are the main points:

GAO was asked to (1) describe the results of recent studies on the consequences of an LNG spill and (2) identify the areas of agreement and disagreement among experts on those consequences. GAO, among other things, convened an expert panel to discuss the issue.

Six unclassified completed studies GAO reviewed examined the effect of a fire resulting from an LNG spill but produced varying results. Sandia National Laboratories conducted one of the studies and concluded that a good estimate of the heat hazard distance would be about one mile. Federal agencies use this conclusion to assess proposals for new LNG import terminals.

The variations among the studies occurred because researchers had to make modeling assumptions since there are no data for large LNG spills. These assumptions involved the size of the hole in the tanker; the volume of the LNG spilled; and environmental conditions, such as wind and waves. The three studies that considered LNG explosions concluded explosions were unlikely unless the LNG vapors were in a confined space. Only the Sandia study examined the potential for sequential failure of LNG cargo tanks (cascading failure) and concluded that up to three of the ship's five tanks could be involved in such an event and that this number of tanks would increase the duration of the LNG fire.

GAO's expert panel generally agreed on the public safety impact of an LNG spill, but believed further study was needed to clarify the extent of these effects, and suggested priorities for this additional research. Experts agreed that the most likely public safety impact of an LNG spill is the heat hazard of a fire and that explosions are not likely to occur in the wake of an LNG spill. However, experts disagreed on the specific heat hazard and cascading failure conclusions reached by the Sandia study.

The Department of Energy (DOE) has recently funded a study to consider these effects; completion is expected in 2008. DOE's study involves large-scale LNG fire experiments and addresses some, but not all, of the research priorities identified by the GAO expert panel.

The leading unaddressed priority the panel cited was the potential for cascading failure of LNG tanks.

GAO recommends that the Secretary of Energy ensure that DOE incorporates into its LNG study the key issues identified by the expert panel. In reviewing the GAO draft report, DOE agreed with this recommendation.