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Testimony: 

Before the Committee on Homeland Security, House of Representatives: 

United States Government Accountability Office: 

GAO: 

For Release on Delivery: 

Expected at 10:00 a.m. EDT: 

Wednesday, March 21, 2007: 

Maritime security: 

Public Safety Consequences of a Liquefied Natural Gas Spill Need 
Clarification: 

Statement of Jim Wells, Director: 
Natural Resources and Environment: 

GAO-07-633T: 

GAO Highlights: 

Highlights of GAO-07-633T, testimony before the Committee on Homeland 
Security, House of Representatives 

Why GAO Did This Study: 

Liquefied natural gas (LNG) is a supercooled liquid form of natural 
gas. U.S. LNG imports are projected to increase to about 17 percent of 
natural gas supplies by 2030, from about 3 percent today. To meet this 
increase, energy companies have submitted 32 applications for new 
terminals. If a terrorist attack on an LNG tanker caused a spill, 
potential hazards, such as fire, asphyxiation, and explosions, could 
result. The Department of Energy (DOE) recently funded a study to 
conduct small- and large-scale experiments to refine and validate 
models that calculate how heat from large LNG fires would affect the 
public. 

This testimony is based on GAO’s recently released report, Maritime 
Security: Public Safety Consequences of a Terrorist Attack on a Tanker 
Carrying Liquefied Natural Gas Need Clarification (GAO-07-316). To 
prepare this report, GAO examined the results of six recent 
unclassified studies on the effects of an LNG spill and convened a 
panel of 19 experts to identify areas of agreement on the consequences 
of a terrorist attack on an LNG tanker. 

What GAO Found: 

The six studies GAO reviewed examining the potential effect of a fire 
resulting from an LNG spill produced varying results; some studies also 
examined other potential hazards of a large LNG spill and reached 
consistent conclusions on explosions. Specifically, the studies’ 
conclusions about the distance at which 30 seconds of exposure to the 
heat (heat hazard) could burn people ranged from less than 1/3 of a 
mile to about 1-1/4 miles. Sandia National Laboratories (Sandia) 
conducted one of the studies and concluded, based on its analysis of 
multiple attack scenarios, that a good estimate of the heat hazard 
distance would be about 1 mile. Federal agencies use this conclusion to 
assess proposals for new LNG import terminals. The variations among the 
studies occurred because, with no data on large spills from actual 
events, researchers had to make numerous modeling assumptions to scale 
up the existing experimental data for large LNG spills. Three of the 
studies also examined other potential hazards of an LNG spill, 
including LNG vapor explosions and sequential failure of multiple tanks 
on the LNG vessel (cascading failure). All three studies considered LNG 
vapor explosions unlikely unless the vapors were in a confined space. 
Finally, the Sandia study examined the potential for cascading tank 
failure and concluded that only three of the five tanks in a typical 
tanker would potentially be affected, and that such failure would 
increase the duration of the LNG fire. 

GAO’s panel of experts generally agreed on the public safety impact of 
an LNG spill caused by a terrorist attack, disagreed on specific 
conclusions of the Sandia study, and suggested future research 
priorities. Experts agreed that the most likely public safety impact of 
an LNG spill is the heat impact of a fire and that explosions are not 
likely to occur unless LNG vapors are in confined spaces. However, the 
experts did not all agree with the heat hazard and cascading failure 
conclusions reached by the Sandia study. Finally, they suggested 
priorities to guide future research aimed at clarifying uncertainties 
about heat impact distances and cascading failure. DOE’s recently 
funded study involving large-scale LNG fire experiments addresses only 
some of the research priorities the expert panel identified. 

Figure: LNG Tanker Passing Downtown Boston on Its way to Port: 

[see PDF for Image] 

Source: GAO. 

[End of figure] 

What GAO Recommends: 

GAO recommended that DOE incorporate the key issues GAO’s expert panel 
identified, particularly the potential for cascading failure, into its 
current LNG study. DOE concurred with this recommendation. 

[Hyperlink, http://www.gao.gov/cgi-bin/getrpt?GAO-07-633T]. 

To view the full product, including the scope and methodology, click on 
the link above. For more information, contact Jim Wells at (202) 512-
3841 or wellsj@gao.gov. 

[End of section] 

United States Government Accountability Office: 

Washington, DC 20548: 

Mr. Chairman and Members of the Committee: 

I am pleased to be here to discuss the results of our recently released 
report on the public safety consequences of a terrorist attack on a 
tanker carrying liquefied natural gas (LNG).[Footnote 1] As you know, 
LNG is a supercooled liquid form of natural gas, which, if spilled, 
poses potential hazards, such as fire, asphyxiation, and explosions. 
U.S. imports of LNG, now about 3 percent of total U.S. natural gas 
supplies, are projected to be about 17 percent of U.S. supplies by 
2030. To meet this increased demand, energy companies have submitted 32 
applications to federal regulators to build new terminals for importing 
LNG in 10 states and 5 offshore areas. Access to accurate information 
about the consequences of LNG spills is crucial for developing risk 
assessments for LNG siting decisions. Despite several recent modeling 
studies of the consequences of potential LNG spills, uncertainties 
remain about the risks such spills would pose to the public. One of 
these studies, conducted by Sandia National Laboratories (Sandia) in 
2004, is used by the Coast Guard to assess the suitability of waterways 
for LNG tankers traveling to proposed LNG facilities. In this context, 
DOE has recently funded a new study that will conduct small-and large- 
scale LNG fire experiments to refine and validate existing models that 
calculate how heat from large LNG fires would affect the public. 

My testimony today summarizes the results of our report. Specifically, 
I will (1) describe the results of recent unclassified studies on the 
consequences of an LNG spill and (2) identify the areas of agreement 
and disagreement among experts concerning the consequences of a 
terrorist attack on an LNG tanker. To address these issues, we examined 
six unclassified studies of the consequences of LNG spills. We also 
convened a Web-based panel of 19 experts to identify areas of agreement 
and disagreement on LNG spill consequence issues. Because some 
additional studies are classified, we will be issuing a separate 
classified report with related findings at a later date. 

Summary: 

The six unclassified studies we reviewed all examined the heat impact 
of an LNG fire but produced varying results; some studies also examined 
other potential hazards of a large LNG spill and reached consistent 
conclusions on explosions. Specifically, the studies' conclusions about 
the distance at which 30 seconds of exposure to the heat could burn 
people--also termed the heat impact distance--ranged from less than 1/ 
3 of a mile to about 1-1/4 miles. These variations occurred because, 
with no data on large spills from actual events, researchers had to 
make numerous modeling assumptions to scale up the existing 
experimental data for large LNG spills. These assumptions involved the 
size of the hole in the tanker, the number of tanks that fail, the 
volume of LNG spilled, key LNG fire properties, and environmental 
conditions, such as wind and waves. Three of the studies also examined 
other potential hazards of an LNG spill, including LNG vapor 
explosions, asphyxiation, and the sequential failure of multiple tanks 
on the LNG vessel (cascading failure). All three studies considered LNG 
vapor explosions unlikely unless the vapors were in a confined space. 
Only the Sandia study examined asphyxiation and concluded that 
asphyxiation did not pose a hazard to the general public. Finally, only 
the Sandia study examined the potential for cascading failure of LNG 
tanks and concluded that only three of the five tanks on a typical LNG 
vessel would be involved in such an event and that this number of tanks 
would increase the duration of the LNG fire. 

Our panel of 19 experts generally agreed on the public safety impact of 
an LNG spill, disagreed on specific conclusions of the Sandia study, 
and suggested future research priorities. Experts agreed on three main 
points: (1) the most likely public safety impact of an LNG spill is the 
heat impact of a fire; (2) explosions are not likely to occur in the 
wake of an LNG spill unless the LNG vapors are in confined spaces; and 
(3) some hazards, such as freeze burns and asphyxiation, do not pose a 
hazard to the public. However, the experts disagreed with a few 
conclusions reached by the Sandia study that the Coast Guard uses to 
assess the suitability of waterways for LNG tankers going to proposed 
LNG terminals. Specifically, all experts did not agree with the study's 
1-mile estimate of heat impact distance resulting from an LNG fire: 7 
of 15 thought Sandia's distance was "about right," 8 were evenly split 
on whether the distance was "too conservative" or "not conservative 
enough," and 4 did not answer this question. Experts also did not agree 
with the Sandia National Laboratories' conclusion that only three of 
the five LNG tanks on a tanker would be involved in a cascading 
failure. Finally, experts suggested priorities to guide future research 
aimed at clarifying uncertainties about heat impact distances and 
cascading failure, including large-scale fire experiments, large-scale 
LNG spill experiments on water, the potential for cascading failure of 
multiple LNG tanks, and improved modeling techniques. DOE's recently 
funded study involving large-scale LNG fire experiments addresses some, 
but not all, of the research priorities the expert panel identified. 

Background: 

As scientists and the public have noted, an LNG spill could pose 
potential hazards. When LNG is spilled from a tanker, it forms a pool 
of liquid on the water. As the liquid warms and changes into natural 
gas, it forms a visible, foglike vapor cloud close to the water. The 
cloud mixes with ambient air as it continues to warm up, and eventually 
the natural gas disperses into the atmosphere. Under certain 
atmospheric conditions, however, this cloud could drift into populated 
areas before completely dispersing. Because an LNG vapor cloud 
displaces the oxygen in the air, it could potentially asphyxiate people 
who come into contact with it. Furthermore, like all natural gas, LNG 
vapors can be flammable, depending on conditions. If the LNG vapor 
cloud ignites, the resulting fire will burn back through the vapor 
cloud toward the initial spill. It will continue to burn above the LNG 
that has pooled on the surface--this is known as a pool fire. Small- 
scale experiments to date have shown that LNG fires burn hotter than 
oil fires of the same size. Both the cold temperatures of spilled LNG 
and the high temperatures of an LNG fire have the potential to 
significantly damage the tanker, causing a cascading failure. Such a 
failure could increase the severity of the incident. Finally, concerns 
have been raised about whether an explosion could result from an LNG 
spill. 

The Federal Energy Regulatory Commission is responsible for approving 
applications for onshore LNG terminal sitings, and the U.S. Coast Guard 
is responsible for approving applications for offshore sitings. In 
addition, the Coast Guard reviews an applicant's Waterway Suitability 
Assessment, reaches a preliminary conclusion on whether the waterway is 
suitable for LNG imports, and identifies appropriate strategies that 
reduce the risk posed by the movement of an LNG tanker. 

Studies Identified Different Distances for the Heat Effects of an LNG 
Fire, but Agreed on Other LNG Hazards: 

The six studies we examined identified various distances at which the 
heat effects of an LNG fire could be hazardous to people. The studies' 
results about the distance at which 30 seconds of exposure to the heat 
could burn people ranged from less than 1/3 of a mile (about 500 
meters) to about 1-1/4 miles (more than 2,000 meters). The studies' 
variations in heat effects occurred because (1) different assumptions 
were made in the studies' models about key parameters of LNG spills and 
(2) the studies were designed and conducted for different purposes. 
Since no large-scale data are available for LNG spills, researchers 
made numerous modeling assumptions to scale up the existing 
experimental data for large spills. Key assumptions made included hole 
size and cascading failure, waves and wind, the volume of LNG spilled, 
and the amount of heat radiated from the fire. For example, studies 
made assumptions for the size of the hole in the LNG tanker that varied 
from less than 1 square meter up to 20 square meters. Additionally, the 
studies were conducted for different purposes. Two studies were 
academic analyses of the differences between LNG and oil spills; three 
specifically addressed spills caused by terrorist attacks, which was a 
concern in the wake of the September 11 attacks; and the final study 
developed appropriate methods for regulators to use to estimate heat 
hazards from LNG fires. Results of these studies can be found in our 
report being released today. 

Some studies also examined other potential hazards, such as explosions, 
asphyxiation, and cascading failure, and identified their potential 
impacts on public safety. Three studies examined the potential for LNG 
vapor explosions, and all agreed that it is unlikely that LNG vapors 
could explode if the vapors are in an unconfined space. Only one study 
examined the potential for asphyxiation following an LNG spill if the 
vapors displace the oxygen in the air. It concluded that fire hazards 
would be the greatest problem in most locations, but that asphyxiation 
could threaten the ship's crew, pilot boat crews, and emergency 
response personnel. Finally, only the Sandia study examined the 
potential for cascading failure of LNG tanks and concluded that only 
three of the five tanks would be involved in such an event and that 
this number of tanks would increase the duration of the LNG fire. 

Experts Generally Agreed That the Most Likely Public Safety Impact of 
an LNG Spill Is the Heat Effect of a Fire, but That Further Study Is 
Needed to Clarify the Extent of This Effect: 

The 19 experts on our panel generally agreed on the public safety 
impact of an LNG spill, disagreed with specific conclusions of the 
Sandia study, and suggested future research priorities.[Footnote 2] 
Specifically: 

* Experts agreed that the main hazard to the public from a pool fire is 
the heat from the fire, but emphasized that the exact hazard distance 
depends on site-specific weather conditions; composition of the LNG 
(relative percentages of methane, propane, and butane); and the size of 
the fire. 

* Eighteen of 19 experts agreed that the ignition of a vapor cloud over 
a populated area could burn people and property in the immediate 
vicinity of the fire. Three experts emphasized in their comments that 
the vapor cloud is unlikely to penetrate very far into a populated area 
before igniting. 

* With regard to explosions, experts distinguished between explosions 
in confined spaces and in unconfined spaces. For confined spaces, such 
as under a dock or between the hulls of a ship, they agreed that it is 
possible, under controlled experimental conditions, to induce 
explosions of LNG vapors; however, a detonation--the more serious type 
of vapor cloud explosion--of confined LNG vapors is unlikely following 
an LNG spill caused by a terrorist attack. For unconfined spaces, 
experts were split on whether it is possible to induce such explosions 
under controlled experimental conditions; however, even experts who 
thought such explosions were possible agreed that vapor cloud 
explosions in unconfined spaces are unlikely to occur following an LNG 
spill caused by a terrorist attack. 

Our panel of 19 experts disagreed with a few of the Sandia study's 
conclusions and agreed with the study authors' perspective on risk- 
based approaches to dealing with the hazards of potential LNG spills. 
For example: 

* Seven of 15 experts thought Sandia's heat hazard distance was "about 
right," and the remaining 8 experts were evenly split as to whether the 
distance was "too conservative" (i.e., larger than needed to protect 
the public) or "not conservative enough" (i.e., too small to protect 
the public). Officials at Sandia National Laboratories and our panel of 
experts cautioned that the hazard distances presented cannot be applied 
to all sites because of the importance of site-specific factors. 
Additionally, two experts explained that there is no "bright line" for 
hazards--that is, 1,599 meters is not necessarily "dangerous," and 
1,601 meters is not necessarily "safe." 

* Nine of 15 experts agreed with Sandia's conclusion that only three of 
the five LNG tanks on a tanker would be involved in cascading failure. 
Five experts noted that the Sandia study did not explain how it 
concluded that only three tanks would be involved in cascading failure. 

* Finally, experts agreed with Sandia's conclusion that consequence 
studies should be used to support comprehensive, risk-based management 
and planning approaches for identifying, preventing, and mitigating 
hazards from potential LNG spills. 

The experts also suggested priorities for future research--some of 
which are not fully addressed in DOE's ongoing LNG research--to clarify 
uncertainties about heat impact distances and cascading failure. These 
priorities include large-scale fire experiments, large-scale LNG spill 
experiments on water, the potential for cascading failure of multiple 
LNG tanks, and improved modeling techniques. As part of DOE's ongoing 
research, Sandia plans to conduct large-scale LNG pool fire tests, 
beginning with a pool size of 35 meters--the same size as the largest 
test conducted to date. Sandia will validate the existing 35-meter data 
and then conduct similar tests for pool sizes up to 100 meters. Of the 
top 10 LNG research priorities the experts identified, only 3 have been 
funded in the DOE study, and the second highest ranked priority, 
cascading failure, was not funded. One expert noted that although the 
consequences of cascading failure could be serious, because the extreme 
cold of spilled LNG and the high heat of an LNG fire could damage the 
tanker, there are virtually no data looking at how a tanker would be 
affected by these temperatures. 

Conclusions: 

It is likely that the United States will increasingly depend on LNG to 
meet its demand for natural gas. Consequently, understanding and 
resolving the uncertainties surrounding LNG spills is critical, 
especially in deciding where to locate LNG facilities. While there is 
general agreement on the types of effects of an LNG spill, the study 
results have created what appears to be conflicting assessments of the 
specific heat consequences of such a spill. These assessments create 
uncertainty for regulators and the public. Additional research to 
resolve some key areas of uncertainty could benefit federal agencies 
responsible for making informed decisions when approving LNG terminals 
and protecting existing terminals and tankers, as well as providing 
reliable information to citizens concerned about public safety. 

To provide the most comprehensive and accurate information for 
assessing the public safety risks posed by tankers transiting to 
proposed LNG facilities, we recommended that the Secretary of Energy 
ensure that DOE incorporates the key issues the expert panel 
identified, particularly the potential for cascading failure, into its 
current LNG study. 

DOE concurred with our recommendation. 

Mr. Chairman, this concludes my prepared statement. I would be happy to 
respond to any questions that you or Members of the Committee may have. 

Contacts and Acknowledgments: 

For further information about this testimony, please contact me at 
(202) 512-3841 or wellsj@gao.gov. James W. Turkett, Janice M. Poling, 
and Carol Herrnstadt Shulman also made key contributions to this 
statement. 

FOOTNOTES 

[1] GAO, Maritime Security: Public Safety Consequences of a Terrorist 
Attack on a Tanker Carrying Liquefied Natural Gas Need Clarification, 
GAO-07-316 (Washington, D.C.: Feb. 22, 2007). This report was prepared 
at the request of this Committee, the House Committee on Energy and 
Commerce, and Representative Edward J. Markey. 

[2] We considered experts to be "in agreement" if more than 75 percent 
of them indicated that they completely agreed or generally agreed with 
a given statement. Not all experts commented on every issue discussed. 

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