Maritime Security: Opportunities Exist to Further Clarify the
Consequences of a Liquefied Natural Gas Tanker Spill (07-MAY-07,
GAO-07-840T).
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 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
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.
-------------------------Indexing Terms-------------------------
REPORTNUM: GAO-07-840T
ACCNO: A69165
TITLE: Maritime Security: Opportunities Exist to Further Clarify
the Consequences of a Liquefied Natural Gas Tanker Spill
DATE: 05/07/2007
SUBJECT: Emergency preparedness
Hazardous substances
Homeland security
Importing
Liquefied natural gas
Maritime security
Natural gas
Port security
Research reports
Tankers (Vessels)
Terrorism
Transportation terminals
Water transportation
Public safety
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GAO-07-840T
* [1]Summary
* [2]Background
* [3]Studies Identified Different Distances for the Heat Effects
* [4]Experts Generally Agreed That the Most Likely Public Safety
* [5]Conclusions
* [6]Contacts and Acknowledgments
* [7]PDF6-Ordering Information.pdf
* [8]Order by Mail or Phone
Testimony
Before the Subcommittee on Coast Guard and Maritime Transportation,
Committee on Transportation and Infrastructure, House of Representatives
United States Government Accountability Office
GAO
For Release on Delivery
Expected at 10:00 a.m. EDT
Monday, May 7, 2007
MARITIME SECURITY
Opportunities Exist to Further Clarify the Consequences of a Liquefied
Natural Gas Tanker Spill
Statement of Mark Gaffigan, Acting Director
Natural Resources and Environment
GAO-07-840T
United States Government Accountability Office
Washington, DC 20548
Mr. Chairman and Members of the Subcommittee:
I am pleased to be here to discuss the results of our report on the public
safety consequences of a terrorist attack on a tanker carrying liquefied
natural gas (LNG).^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. Because of
the projected increase in tankers carrying LNG to these terminals, public
safety concerns have been raised, including the consequences of a
terrorist attack. In light of these concerns, 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 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 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, including consideration of a terrorist attack.
^1GAO, 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 the House Committee on Homeland Security, the House Committee on Energy
and Commerce, and Representative Edward J. Markey.
Summary
The six 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.
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.^2 Specifically:
^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.
o 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.
o 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.
o 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:
o 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."
o 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.
o 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 gaffiganm@gao.gov. James W. Turkett, Janice M.
Poling, and Carol Herrnstadt Shulman also made key contributions
to this statement.
(360843)
www.gao.gov/cgi-bin/getrpt?GAO-07-840T .
To view the full product, including the scope
and methodology, click on the link above.
For more information, contact Mark Gaffigan at (202) 512-3841 or
gaffiganm@gao.gov.
Highlights of [10]GAO-07-840T , testimony before the Subcommittee on Coast
Guard and Maritime Transportation, Committee on Transportation and
Infrastructure, House of Representatives
May 2007
MARITIME SECURITY
Opportunities Exist to Further Clarify the Consequences of a Liquefied
Natural Gas Tanker Spill
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 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 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.
[11]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.
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 studies considered LNG vapor explosions and
concluded that such explosions are unlikely unless the vapors were in a
confined space. Only the Sandia study examined the potential for the
sequential failure of multiple tanks on the LNG vessel (cascading 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 expert panel 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.
LNG Tanker Passing Downtown Boston on Its Way to Port
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10. http://www.gao.gov/cgi-bin/getrpt?GAO-07-840T
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