Maritime Security: Public Safety Consequences of a Terrorist	 
Attack on a Tanker Carrying Liquefied Natural Gas Need		 
Clarification (22-FEB-07, GAO-07-316).				 
                                                                 
The United States imports natural gas by pipeline from Canada and
by tanker as liquefied natural gas (LNG) from overseas. LNG--a	 
supercooled form of natural gas--currently accounts for about 3  
percent of total U.S. natural gas supply, with an expected	 
increase to about 17 percent by 2030, according to the Department
of Energy (DOE). With this projected increase, many more LNG	 
import terminals have been proposed. However, concerns have been 
raised about whether LNG tankers could become terrorist targets, 
causing the LNG cargo to spill and catch on fire, and potentially
explode. DOE has recently funded a study to consider these	 
effects; completion is expected in 2008. 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 concerning the consequences of a	 
terrorist attack on an LNG tanker. To address these objectives,  
GAO, among other things, convened an expert panel to discuss the 
consequences of an attack on an LNG tanker.			 
-------------------------Indexing Terms------------------------- 
REPORTNUM:   GAO-07-316 					        
    ACCNO:   A66105						        
  TITLE:     Maritime Security: Public Safety Consequences of a       
Terrorist Attack on a Tanker Carrying Liquefied Natural Gas Need 
Clarification							 
     DATE:   02/22/2007 
  SUBJECT:   Emergency preparedness				 
	     Hazardous substances				 
	     Homeland security					 
	     Importing						 
	     Liquefied natural gas				 
	     Maritime security					 
	     Natural gas					 
	     Port security					 
	     Research reports					 
	     Ships						 
	     Tanks (containers) 				 
	     Terrorism						 
	     Transportation terminals				 
	     Water transportation				 
	     Public safety					 

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GAO-07-316

   

     * [1]Results in Brief
     * [2]Background
     * [3]Studies Identified Different Distances for the Heat Effects

          * [4]Studies Identified Various Distances That the Heat Effects o
          * [5]Some Studies Examined Other Potential Hazards and Identified

     * [6]Experts Generally Agreed That the Most Likely Public Safety

          * [7]Experts Agreed That the Heat from an LNG Fire Was Most Likel
          * [8]Experts Disagreed with a Few Key Conclusions of the Sandia N
          * [9]Experts Suggest Future Research Priorities to Determine the

     * [10]Conclusions
     * [11]Recommendation for Executive Action
     * [12]Agency Comments and Our Evaluation

          * [13]Introduction
          * [14]LNG Hazards

               * [15]Overall Hazards
               * [16]LNG Hazards-Freeze Burns
               * [17]LNG Hazards-Asphyxiation
               * [18]LNG Hazards-Vapor Cloud: Wind Effect
               * [19]LNG Hazards-Fire Hazard
               * [20]LNG Hazards-Fire Hazard: Thermal Hazard End Point
               * [21]LNG Hazards-Fire Hazard: Pool Fire
               * [22]LNG Hazards-Vapor Cloud Fire
               * [23]LNG Hazards-Vapor Cloud Fire: Burn Back Speed
               * [24]Explosions-RPT
               * [25]Explosions-Deflagrations and Detonations
               * [26]Explosions--Deflagrations, Detonations, and BLEVEs
               * [27]LNG Hazards-Is BLEVE the Worst?

          * [28]Questions About the 2004 Sandia National Laboratories Study
          * [29]Commodity Comparison
          * [30]Future Research

     * [31]GAO Contact
     * [32]Staff Acknowledgments
     * [33]GAO's Mission
     * [34]Obtaining Copies of GAO Reports and Testimony

          * [35]Order by Mail or Phone

     * [36]To Report Fraud, Waste, and Abuse in Federal Programs
     * [37]Congressional Relations
     * [38]Public Affairs

Report to Congressional Requesters

United States Government Accountability Office

GAO

February 2007

MARITIME SECURITY

Public Safety Consequences of a Terrorist Attack on a Tanker Carrying
Liquefied Natural Gas Need Clarification

GAO-07-316

Contents

Letter 1

Results in Brief 7
Background 8
Studies Identified Different Distances for the Heat Effects of an LNG Fire
11
Experts Generally Agreed That the Most Likely Public Safety Impact of an
LNG Spill Is Fire's Heat Effect, but That Further Study Is Needed to
Clarify the Extent of This Effect 17
Conclusions 22
Recommendation for Executive Action 23
Agency Comments and Our Evaluation 23
Appendix I Scope and Methodology 24
Appendix II Names and Affiliations of Members of GAO's Expert Panel on LNG
Hazards 26
Appendix III Summary of Expert Panel Results 27
Appendix IV GAO Contact and Staff Acknowledgments 41

Tables

Table 1: Key Assumptions and Results of the LNG Spill Consequence Studies
13
Table 2: Expert Panel's Ranking of Need for Research on LNG 21

Figures

Figure 1: Existing, Approved, and Proposed LNG Terminals in the United
States, as of October 2006 3
Figure 2: LNG Membrane Tanker 11

This is a work of the U.S. government and is not subject to copyright
protection in the United States. It may be reproduced and distributed in
its entirety without further permission from GAO. However, because this
work may contain copyrighted images or other material, permission from the
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separately.

Abbreviations

BLEVE boiling liquid expanding vapor explosion
DOE Department of Energy
DOT Department of Transportation
FERC Federal Energy Regulatory Commission
kW/m^2 kilowatts per square meter
LNG liquefied natural gas
LPG liquefied petroleum gas
m^2 square meters
m^3 cubic meters
m/s meters per second
RPT rapid phase transition
WSA Waterway Suitability Assessment

United States Government Accountability Office

Washington, DC 20548

February 22, 2007 

The Honorable John D. Dingell
Chairman
The Honorable Joe Barton
Ranking Member
Committee on Energy and Commerce
House of Representatives

The Honorable Bennie G. Thompson
Chairman
The Honorable Peter King
Ranking Member
Committee on Homeland Security
House of Representatives

The Honorable Edward J. Markey
House of Representatives

Worldwide, over 40,000 tanker cargos of liquefied natural gas (LNG) have
been shipped since 1959, and imports of LNG are projected to increase over
the next 10 years. LNG is a supercooled liquid form of natural gas--a
crucial source of energy for the United States. Natural gas is used in
homes for cooking and heating and as fuel for generating electricity, and
it accounts for about one-fourth of all energy consumed in the United
States each year. Prices for natural gas in the United States have risen
over the past 5 years as demand for natural gas has increased faster than
domestic production. To make up for the domestic shortfall, the United
States imports some natural gas in pipelines from Canada. However, most
reserves of natural gas are overseas and cannot be transported through
pipelines. Natural gas from these reserves has to be transported to the
United States as LNG in tankers. Because of the projected increase in LNG
tankers arriving at U.S. ports, concerns have been raised about whether
the tankers could become terrorist targets. Worldwide, over 40,000 tanker
cargos of liquefied natural gas (LNG) have been shipped since 1959, and
imports of LNG are projected to increase over the next 10 years. LNG is a
supercooled liquid form of natural gas--a crucial source of energy for the
United States. Natural gas is used in homes for cooking and heating and as
fuel for generating electricity, and it accounts for about one-fourth of
all energy consumed in the United States each year. Prices for natural gas
in the United States have risen over the past 5 years as demand for
natural gas has increased faster than domestic production. To make up for
the domestic shortfall, the United States imports some natural gas in
pipelines from Canada. However, most reserves of natural gas are overseas
and cannot be transported through pipelines. Natural gas from these
reserves has to be transported to the United States as LNG in tankers.
Because of the projected increase in LNG tankers arriving at U.S. ports,
concerns have been raised about whether the tankers could become terrorist
targets.

LNG--primarily composed of methane--is odorless and nontoxic. It is
produced by supercooling natural gas to minus 260 degrees Fahrenheit at
atmospheric pressure, thus reducing its volume by more than 600 times.
This process makes transport by tankers feasible. The tankers are
double-hulled, with each tanker containing between four and six adjacent
tanks heavily insulated to maintain the LNG's supercool temperature.
Generally, LNG--primarily composed of methane--is odorless and nontoxic.
It is produced by supercooling natural gas to minus 260 degrees Fahrenheit
at atmospheric pressure, thus reducing its volume by more than 600 times.
This process makes transport by tankers feasible. The tankers are
double-hulled, with each tanker containing between four and six adjacent
tanks heavily insulated to maintain the LNG's supercool temperature.
Generally, these ships can carry enough LNG to supply the daily energy
needs of over 10 million homes. Importing LNG requires specialized
facilities--called regasification terminals--at ports of entry. At these
terminals, the liquid is reconverted into natural gas and then injected
into the pipeline system for consumers. Currently, the United States has a
total of five LNG import terminals--four are considered onshore terminals,
that is, they are located within 3 miles of the shore; one is an offshore
terminal located 116 miles off the Louisiana coast in the Gulf of
Mexico.^1

The United States imports about 3 percent of its total natural gas supply
as LNG in recent years, but by 2030, LNG imports are projected to account
for about 17 percent of the U.S. natural gas supply, according to the
Department of Energy's (DOE) Energy Information Administration. To meet
this increased demand, energy companies have submitted 32 applications to
build new terminals for importing LNG in 10 states and five offshore
areas. Figure 1 shows the locations of LNG terminals that are operational,
approved, and proposed.

^1The onshore facilities are near Boston, Massachusetts; Cove Point,
Maryland; Savannah, Georgia; and Lake Charles, Louisiana. The United
States also has one LNG export facility in Kenai, Alaska, that ships LNG
to Japan.

Figure 1: Existing, Approved, and Proposed LNG Terminals in the United
States, as of October 2006

As of October 2006, the Federal Energy Regulatory Commission
(FERC)^2--responsible for approving onshore LNG terminal siting
applications--and the U.S. Coast Guard^3--responsible for approving
offshore LNG terminal siting applications--had together approved 13 of
these applications. In addition, the Coast Guard contributes to FERC's
review of onshore LNG facilities by reviewing and validating an
applicant's Waterway Suitability Assessment (WSA) and reaching a
preliminary conclusion as to whether the waterway is suitable for LNG
operations with regard to navigational safety and security considerations.
The WSA includes a security risk assessment to evaluate the public safety
risk of an LNG spill from a tanker following an attack. The security risk
assessment analyzes potential types of attacks, their probability, and the
potential consequences. The WSA also identifies appropriate strategies
that can be used to reduce the risk posed by a terrorist attack on an LNG
tanker, either by reducing the probability of an attack, or by reducing
its consequences. If the WSA deems the waterway suitable for LNG tanker
traffic, the Coast Guard provides FERC with a "Letter of Recommendation,"
which describes the overall risk reduction strategies that will be used on
LNG tankers traveling to the proposed terminal. The Coast Guard is the
lead federal agency for ensuring the security of active LNG import
terminals and tankers traveling within U.S. ports.

As figure 1 shows, six new facilities have been proposed for the
northeastern United States, a region that faces gas supply challenges. The
Northeast has limited indigenous supplies of natural gas, and receives
most of its natural gas either through pipelines from the U.S. Gulf Coast
or Canada, or from overseas via tanker as LNG. The pipelines into the
Northeast currently run at or near capacity for much of the winter, and
demand is projected to significantly increase over the next 5 years,
exceeding available supply by 2010. To meet the increasing demand, new
supplies of natural gas must reach the Northeast by expanding existing
pipeline capacity, constructing new pipelines, or constructing new LNG
terminals--all of which have risk associated with them. Difficulties
siting LNG facilities in the Northeast could lead to higher natural gas
prices unless additional supply can be brought into the region via new, or
expansion of old, pipelines.

^2Under the Natural Gas Act, as amended, FERC has exclusive authority to
approve or deny an application for the siting, construction, or operation
of onshore LNG terminals, including pipelines, and offshore facilities in
state waters--that is, generally within 3 miles of shore.

^3The Coast Guard, along with the Department of Transportation's Maritime
Administration, has jurisdiction under the Deep Water Port Act of 1974, as
amended, to approve the siting and operation of offshore LNG facilities in
federal waters.

Scientists and the public have raised concerns about the potential hazards
that an LNG spill could pose. When LNG is spilled from a tanker, it forms
a pool of liquid on the water. Individuals who come into contact with LNG
could experience freeze burns. 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.^4 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. 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 multiple tanks on the ship to
fail in sequence--called 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.

Although LNG tankers have carried over 40,000 shipments worldwide since
1959, there have been no LNG spills resulting from a cargo tank rupture.
Some safety incidents, such as groundings or collisions, have resulted in
small LNG spills that did not affect public safety. In the 1970s and
1980s, experiments to determine the consequences of a spill examined small
LNG spills of up to 35 meters in diameter. Following the terrorist attacks
of September 11, 2001, however, many experts recognized that an attack on
an LNG tanker could result in a large spill--a volume of LNG up to 100
times greater than studied in past experiments. Since then, a number of
studies have reevaluated safety hazards of LNG tankers in light of a
potential terrorist threat. Because a major LNG spill has never occurred,
studies examining LNG hazards rely on computer models to predict the
effects of hypothetical accidents, often focusing on the properties of LNG
vapor fires. The Coast Guard uses one of these studies, conducted in 2004
by Sandia National Laboratories,^5 as a basis for conducting the security
risk assessment required in the WSA for proposed onshore LNG facilities.^6
Access to accurate information about the consequences of LNG spills is
crucial for developing accurate risk assessments for LNG siting decisions.
While an underestimation of the consequences could expose the public to
additional risk in the event of an LNG spill, an overestimation of
consequences could result in the use of inappropriate and costly risk
mitigation strategies. DOE recently funded a new study--to be completed by
Sandia National Laboratories in 2008--that will conduct small- and
large-scale LNG fire experiments to refine and validate existing models
(such as the one used by Sandia National Laboratories in their 2004 study)
that calculate the heat hazards of large LNG fires.

^4LNG vapors only ignite when they are in a 5 percent to 15 percent
concentration in the air. If the LNG concentration is higher, there is not
enough oxygen available for fire. If the concentration is lower, there is
likewise not enough fuel for fire.

In this context, you asked us to (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 the first objective, we identified eight unclassified,
completed studies of LNG hazards and reviewed the six studies that
included new, original research (either experimental or modeling) and
clearly described the methodology used. While we have not verified the
scientific modeling or results of these studies, the methods used seem
appropriate for the work conducted. We also interviewed agencies
responsible for LNG regulations and visited all four onshore LNG import
facilities and one export facility. To address the second objective, we
identified 19 recognized experts in LNG hazard analysis and convened a
Web-based expert panel to obtain their views on LNG hazards and to get
agreement on as many issues as possible. In selecting experts for the
panel, we sought individuals who are widely recognized as having
experience with one or more key aspects of LNG hazard analysis. We sought
to achieve balance in representation from government, academia,
consulting, research organizations, and industry. Additionally, we ensured
that our expert panel included at least one author from each of the six
unclassified studies of LNG hazards. Because some of the studies conducted
are classified, this public version of our findings supplements a more
comprehensive classified report produced under separate cover. A more
detailed description of our scope and methodology is presented in appendix
I. We conducted our work from January 2006 through January 2007 in
accordance with generally accepted government auditing standards.

^5Sandia National Laboratories. Guidance on Risk Analysis and Safety
Implications of a Large Liquefied Natural Gas (LNG) Spill Over Water.
Albuquerque: 2004.

^6DOE is also sponsoring additional research that applies the 2004 Sandia
National Laboratories' methodology to LNG tankers larger than those
previously studied, which is expected to be completed in July 2007.

Results in Brief

The six unclassified studies we reviewed all examined the heat impact of
an LNG pool 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
ranged from about 500 meters (less than 1/3 of a mile) to more than 2,000
meters (about 1-1/4 miles). The Sandia National Laboratories' study
concluded that the most likely distance for a burn is about 1,600 meters
(1 mile). These variations occurred because researchers had to make
numerous modeling assumptions to scale-up the existing experimental data
for large LNG spills since there are no large spill data from actual
events. 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 cascading failure. All
three studies considered LNG vapor explosions unlikely unless the LNG
vapors were in a confined space. Only the Sandia National Laboratories'
study examined asphyxiation, and it concluded that asphyxiation did not
pose a hazard to the general public. Finally, only the Sandia National
Laboratories' 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.

Our panel of 19 experts generally agreed on the public safety impact of an
LNG spill, disagreed with a few conclusions reached by the Sandia National
Laboratories' study, and suggested priorities for research to clarify the
impact of heat and cascading tank failures. Experts agreed that (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.
Experts disagreed with the heat impact and cascading tank failure
conclusions reached by the Sandia National Laboratories' study, which the
Coast Guard uses to prepare WSAs. Specifically, all experts did not agree
with the heat impact distance of 1,600 meters. Seven of 15 experts thought
Sandia's distance was "about right," and the remaining eight experts were
evenly split as to whether the distance was "too conservative" or "not
conservative enough" (the other 4 experts 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 identified by the expert
panel.

We are recommending that DOE incorporate into its current LNG study the
key issues identified by the expert panel. We particularly recommend that
DOE examine the potential for cascading failure of LNG tanks.

Background

Natural gas is primarily composed of methane, with small percentages of
other hydrocarbons, including propane and butane. When natural gas is
cooled to minus 260 degrees Fahrenheit at atmospheric pressure, the gas
becomes a liquid, known as LNG, and it occupies only about 1/600th of the
volume of its gaseous state. Since LNG is maintained in an extremely
cooled state--reducing its volume--there is no need to store it under
pressure. This liquefaction process allows natural gas to be transported
by trucks or tanker vessels. LNG is not explosive or flammable in its
liquid state. When LNG is warmed, either at a regasification terminal or
from exposure to air as a result of a spill, it becomes a gas. As this gas
mixes with the surrounding air, a visible, low-lying vapor cloud results.
This vapor cloud can be ignited and burned only within a minimum and
maximum concentration of air and vapor (percentage by volume). For
methane, the dominant component of this vapor cloud, this flammability
range is between 5 percent and 15 percent by volume. When fuel
concentrations exceed the cloud's upper flammability limit, the cloud
cannot burn because too little oxygen is present. When fuel concentrations
are below the lower flammability limit, the cloud cannot burn because too
little methane is present. As the cloud vapors continue to warm, above
minus 160 degrees Fahrenheit, they become lighter than air and will rise
and disperse rather than collect near the ground.

If the cloud vapors ignite, the resulting fire will burn back through the
vapor cloud toward the initial spill and will continue to burn above the
LNG that has pooled on the surface. This fire burns at an extremely high
temperature--hotter than oil fires of the same size. LNG fires burn hotter
because the flame burns very cleanly and with little smoke. In oil fires,
the smoke emitted by the fire absorbs some of the heat from the fire and
reduces the amount of heat emitted. Scientists measure the amount of heat
given off by a fire by looking at the amount of heat energy emitted per
unit area as a function of time. This is called the surface emissive power
of a fire and is measured in kilowatts per square meter (kW/m^2).
Generally, the heat given off by an LNG fire is reported to be more than
200 kW/m^2. By comparison, the surface emissive power of a very smoky oil
fire can be as little as 20 kW/m^2. The heat from fire can be felt far
away from the fire itself. Scientists use heat flux--also measured in
kW/m^2--to quantify the amount of heat felt at a distance from a fire. For
instance, a heat flux of 5 kW/m^2 can cause second degree burns after
about 30 seconds of exposure to bare skin. This heat flux can be compared
with the heat from a candle--if a hand is held about 8 to 9 inches above
the candle, second degree burns could result in about 30 seconds. A heat
flux of about 12.5 kW/m^2, over an exposure time of 10 minutes, will
ignite wood, and a heat flux of about 37.5 kW/m^2 can damage steel
structures.

Four types of explosions could potentially occur after an LNG spill: rapid
phase transitions (RPT), deflagrations, detonations, and
boiling-liquid-expanding-vapor-explosions (BLEVE).^7 More specifically:

           o An RPT occurs when LNG is warmed and changes into natural gas
           nearly instantaneously. An RPT generates a pressure wave that can
           range from very small to large enough to damage lightweight
           structures. RPTs strong enough to damage test equipment have
           occurred in past LNG spill experiments on water, although their
           effects have been localized at the site of the RPT.
           o Deflagrations and detonations are explosions that involve
           combustion (fire). They differ on the basis of the speed and
           strength of the pressure wave generated: deflagrations move at
           subsonic velocities and can result in pressures (overpressures) up
           to 8 times higher than the original pressure; detonations travel
           faster--at supersonic velocities--and can result in larger
           overpressures--up to 20 times the original pressure. Methane does
           not detonate as readily as other hydrocarbons; it requires a
           larger explosion to initiate a detonation in a methane cloud.
           o A BLEVE occurs when a liquefied gas is heated to above its
           boiling point while contained within a tank. For instance, if a
           hot fire outside an LNG tanker sufficiently heated the liquid
           inside, a percentage of the LNG within the tank could "flash" into
           a vapor state virtually instantaneously, causing the pressure
           within the tank to increase. LNG tanks do have pressure relief
           valves, but if these were inadequate or failed, the pressure
           inside the tank could rupture the tank. The escaping gas would be
           ignited by the fire burning outside the tank, and a fireball would
           ensue. The rupture of the tank could create an explosion and
           flying debris (portions of the tank).

           World natural gas reserves are abundant, estimated at about 6,300
           trillion cubic feet, or 65 times the volume of natural gas used in
           2005. Much of this gas is considered "stranded" because it is
           located in regions far from consuming markets. Russia, Iran, and
           Qatar combined hold natural gas reserves that represent more than
           half of the world total. Many countries have imported LNG for
           years. In 2005, 13 countries shipped natural gas to 14
           LNG-importing countries. LNG imports, as a percentage of a
           country's total gas supply, for each of the importing countries
           ranged from 3 percent in the United States to nearly 95 percent in
           Japan. In 2005, LNG imports to the United States originated
           primarily in Trinidad and Tobago (70 percent), Algeria (15
           percent), and Egypt (11 percent). The remaining 4 percent of U.S.
           LNG imports came from Oman, Malaysia, Nigeria, and Qatar.

           LNG tankers primarily have two basic designs, called membrane or
           Moss (see fig. 2). Both designs consist of an outer hull, inner
           hull, and cargo containment system. In membrane tank designs, the
           cargo is contained by an Invar, or stainless steel double-walled
           liner, that is structurally supported by the vessel's inner hull.
           The Moss tank design uses structurally independent spherical or
           prismatic shaped tanks. These tanks, usually five located one
           behind the other, are constructed of either stainless steel or an
           aluminum alloy. LNG tankers ships are required to meet
           international maritime construction and operating standards, as
           well as U.S. Coast Guard safety and security regulations.

           Figure 2: LNG Membrane Tanker
			  
			  Studies Identified Different Distances for the Heat Effects of an
			  LNG Fire

           The six studies we examined identified various distances at which
           the heat effects of an LNG fire could be hazardous to people. The
           studies' variations in heat effects result from the assumptions
           made in the studies' models. Some studies also examined other
           potential hazards such as LNG vapor explosions, other types of
           explosions, and asphyxiation, and identified their potential
           impacts on public safety.
			  
			  Studies Identified Various Distances That the Heat Effects of an
			  LNG Fire Could Be Hazardous to People because of Assumptions Made

           The studies' conclusions about the distance at which 30 seconds of
           exposure to the heat could burn people ranged from about 500
           meters (less than 1/3 mile) to more than 2,000 meters (about 1-1/4
           miles). The results--size of the LNG pool, the duration of the
           fire, and the heat hazard distance for skin burn--varied in part
           because the studies made different assumptions about key
           parameters of LNG spills and also because they were designed and
           conducted for different purposes. Key assumptions made included
           the following:

           o Hole size and cascading failure. Hole size is an important
           parameter for modeling LNG spills because of its relationship to
           the duration of the event--larger holes allow LNG to spill from
           the tanker more quickly, resulting in larger LNG pools and shorter
           duration fires. Conversely, small holes could create
           longer-duration fires. Cascading failure is important because it
           increases the overall spill volume and the duration of the spill.
           o Waves and wind. These conditions can affect the size of both the
           LNG pool and the heat hazard zone. One study indicated that waves
           can inhibit the spread of an LNG pool, keeping the pool size much
           smaller than it would be on a smooth surface, and thereby reducing
           the size of the LNG pool fire. Wind will tend to tilt the fire
           downwind (like a candle flame blowing in the wind), increasing the
           heat hazard zone in that direction (and decreasing it upwind).
           o Volume of LNG spilled. The amount of LNG spilled is one of the
           factors that can affect the size of the pool.
           o Surface emissive power of the fire. While the amount of heat
           given off by a large LNG fire is unknown, assumptions about it
           directly affect the results for the heat hazard zone. It is
           expected that the surface emissive power of LNG fires will be
           lower for large fires because oxygen will not circulate
           efficiently within a very large fire. Lack of oxygen in the middle
           of a large fire would lead to more smoke production, which would
           block some of the heat from the fire.

           The LNG spill consequence studies' key assumptions and results are
           shown in table 1.

^7Generally, an explosion is an energy release associated with a pressure
wave. Some explosions are large enough that the pressure wave can break
windows or damage structures, while others are much smaller.

Table 1: Key Assumptions and Results of the LNG Spill Consequence Studies

                                    Key assumptions                              Key results
                                    Environmental                                                    
                                     conditions                                                      
                                      modeled:                                                       
                                               Wind                                                  
                                              speed                                                  
                                                and                               Distance           
                       Number of                its                Fire             to the           
                      tanks that  Wind speed effect             surface            5kw/m^2           
                 Hole    rupture     and its     on      Spill emissive      Pool     heat           
                 size (cascading   effect on   fire     volume    power  diameter    level  Duration 
                (m^2)    failure  waves(m/s)  (m/s)      (m^3) (kW/m^2)  (meters) (meters) (minutes) 
Quest            19.6          1         1.5    1.5     12,500        b       156      497      14.3 
Consultants     19.6           1    5.0      5.0      12,500          b       146                531    16.6 
Inc. (Quest)^a  19.6           1    9.0      9.0      12,500          b       110                493    28.6 
Sandia              2          3           c      c     37,500      220       209      784        20 
National           5           3      c        c      37,500        220       572              2,118     8.1 
Laboratories       5           1      c        c      12,500        350       330              1,652     8.1 
(Sandia)         5^d           1      c        c      12,500        220   330-405        1,305-1,579 5.4-8.1 
                  12           1      c        c      12,500        220       512              1,920     3.4 
Pitblado, et                                                                                         
al.                                                                                                  
(Pitblado)^e     1.77          1           c    3.0     17,250        b       171      750        32 
ABS Consulting   0.79          1           c    8.9     12,500      265     200^g      650        51 
(ABSC)^f        19.6           1      c      8.9      12,500        265     620^g              1,500     4.2 
Fay (Fay)^h        20          1           c      c     14,300        b         b    1,900       3.3 
Lehr and                                                                                             
Simecek-Beatty                                                                                       
(Lehr)^i            b          b           c      c        500      200         b      500       2-3 

Source: GAO analysis of spill consequence studies.

a"Modeling LNG Spills in Boston Harbor." Copyright(c) 2003 Quest
Consultants, Inc., Norman, OK 73609; Letter from Quest Consultants to DOE
(October 2, 2001); Letter from Quest Consultants to DOE (October 3, 2001).

bInformation not available.

cNot included in the model.

dThe study examined multiple scenarios of 5m^2. The ranges listed
summarize the highest and lowest values for those scenarios.

eR. M. Pitblado, J. Baik, G. J. Hughes, C. Ferro, and S. J. Shaw.
"Consequences of Liquefied Natural Gas Marine Incidents." Process Safety
Progress 24 no. 2 (June 2005).

fABS Consulting Inc. Consequence Assessment Methods for Incidents
Involving Releases from Liquefied Natural Gas Carriers. May 13, 2004. FERC
"Staff's Responses to Comments on the Consequence Assessment Methods for
Incidents Involving Releases from Liquefied Natural Gas Carriers," June
18, 2004.

gABS Consulting modeled pool size as a semicircle and reported the radius
of that semicircle in the study. The reported radii were used to calculate
the diameter of the semicircle so the study results could be compared with
the other studies.

hJ.A. Fay. "Model of Spills and Fires from LNG and Oil tankers." Journal
of Hazardous Materials B96 (2003): 171-188.

IWilliam Lehr and Debra Simecek-Beatty. "Comparison of Hypothetical LNG
and Fuel Oil Fires on Water." Journal of Hazardous Materials 107 (2004):
3-9.

In terms of the studies' results, we identified the following three key
results:

           o Pool size describes the extent of the burning pool--and can help
           people understand how large the LNG fire itself will be.
           o Heat hazard distance describes the distance at which 30 seconds
           of exposure could cause second degree burns.
           o Fire duration of the incident describes how long people and
           infrastructure will be exposed to the heat from the fire. The
           longer the fire, the greater potential for damage to the tanker
           and for cascading failure.

           Although all the studies considered the consequences of an LNG
           spill, they were conducted for different purposes. Three of the
           six studies--Quest, Sandia, and Pitblado--specifically addressed
           the consequences of LNG spills caused by terrorist attacks. Two of
           these three studies--Quest and Sandia--were commissioned by DOE.
           The Quest study, begun in response to the September 11, 2001,
           attacks, was designed to quantify the heat hazard zones for LNG
           tanker spills in Boston Harbor. Only the Quest study examined how
           wind and waves would affect the spreading of the LNG on the water
           and the size of the resulting LNG pool. The Quest study based its
           wind and wave assumptions on weather data from buoys near Boston
           Harbor. The Quest study found that, while the waves would help
           reduce the size of the LNG pool, the winds that created the waves
           would tend to increase the heat hazard distance downwind. To
           simplify the modeling of the waves, the Quest study considered
           "standing" waves (rather than moving waves) of various heights
           and, therefore, did not consider the impact of wave movement on
           LNG pool spreading. The ABSC study expressed concern that Quest's
           standing wave assumption resulted in pool sizes that were too
           small because wave movement might help spread the LNG.

           The 2004 Sandia study was intended to develop guidance on a
           risk-based analysis approach to assess potential threats to an LNG
           tanker, determine the potential consequences of a large spill, and
           review techniques that could be used to mitigate the consequences
           of an LNG spill. The assumptions and results in table 1 for the
           Sandia study refer to the scenarios Sandia examined that had
           terrorist causes. According to Sandia, the study used available
           intelligence and historical data to develop credible and possible
           scenarios for the kinds of attacks that could breach an LNG
           tanker. Sandia then modeled how large a hole each of the weapon
           scenarios could create in an LNG tanker.^8 Two of these
           intentional breach scenarios included cascading failure of three
           tanks on an LNG tanker. In these cases, the LNG spill from one
           tank, as well as the subsequent fire, causes the neighboring two
           tanks to fail on the LNG tanker, resulting in LNG spills from
           three of the five tanks on the tanker. After considering all of
           its scenarios, Sandia concluded that, as a rule-of-thumb, 1,600
           meters is a good approximation of the heat hazard distance for
           terrorist-induced spills. However, as the table shows, one of
           Sandia's scenarios--for a large spill with cascading failure of
           three LNG tanks--found that the distance could exceed more than
           2,000 meters and that the cascading failure would increase the
           duration of the incident.

           Finally, the stated purpose of industry's Pitblado study was to
           develop credible threat scenarios for attacks on LNG tankers and
           predict hazard zones for LNG spills from those types of attacks.
           The study identified a hole size smaller than the other studies
           that specifically considered terrorist attacks.

           The other studies we reviewed examined LNG spills regardless of
           cause. FERC commissioned the ABS Consulting study to develop
           appropriate methods for estimating heat hazard zones from LNG
           spills. FERC uses these methods, in conjunction with the Sandia
           study, to examine the public safety consequences of tankers
           traveling to proposed onshore LNG facilities before granting
           siting approval. The two scenarios in the ABSC study illustrate
           how small holes could result in longer fires, which have a higher
           potential to damage the tanker itself. One scenario used a hole
           size of 0.79 square meters and the other a hole size of about 20
           square meters. The difference in duration is striking--it takes 51
           minutes and 4.2 minutes, respectively, for the fire to consume all
           the spilled LNG.

           Finally, the Lehr and Fay studies compared the fire consequences
           of LNG spills with known information about oil spills and fires.
           Although most studies made similar assumptions about the volume of
           LNG spilled from any single LNG tank, Lehr examined a much smaller
           spill volume--just 500 cubic meters of LNG, compared with a range
           of 12,500 to 17,250 cubic meters.
			  
^8Please note that the information used to develop Sandia's terrorist
scenarios is classified and will be discussed in GAO's classified report.		  
			  
			  Some Studies Examined Other Potential Hazards and Identified Their
			  Impact on Public Safety

           Three of the studies also examined other potential hazards of an
           LNG spill, including LNG vapor explosions, other types of
           explosions, and asphyxiation.

           LNG vapor explosions. Three studies--Sandia, ABSC, and
           Pitblado--examined LNG vapor explosions, and all agreed that it is
           unlikely that LNG vapors could explode and create a pressure wave
           if the vapors are in an unconfined space. Although the three
           studies agreed that LNG vapors could explode only in confined
           areas, they did not conduct modeling or describe the likelihood of
           such confinement after an LNG spill from a tanker. The Sandia
           study stated that fire will generally progress through the vapor
           cloud slowly and without producing an explosion with damaging
           pressure waves. The study did suggest, however, that if the LNG
           vapor cloud is confined (e.g., between the inner and outer hull of
           an LNG carrier), it could explode but would only affect the
           immediate surrounding area. The ABSC study and the Pitblado study
           agreed that a confined LNG vapor cloud could result in an
           explosion.

           Other types of explosions. Three studies--Sandia, ABSC, and
           Pitblado--examined the potential for RPTs. The Sandia study
           concluded that, while RPTs have generated energy releases
           equivalent to several pounds of explosives, RPT impacts will be
           localized near the spill. Sandia also noted that RPTs are not
           likely to cause structural damage to the vessel. The ABSC study
           noted that their literature search suggested that damage from RPT
           overpressures would be limited to the immediate vicinity, though
           it noted that the literature did not include large spills like
           those that could be caused by a terrorist attack. Only one study,
           Pitblado, discussed the possibility of a BLEVE. According to our
           discussions with Dr. Pitblado, an LNG ship with membrane tanks
           could not result in a BLEVE, but he said that Moss spherical tanks
           could potentially result in a BLEVE. A BLEVE could result because
           it is possible for pressure to build up in a Moss tanker. A 2002
           LNG tanker truck incident in Spain resulted in an explosion that
           some scientists have characterized as a BLEVE of an LNG truck.
           Portions of the tanker truck were found 250 meters from the
           accident itself, propelled by the strength of the blast.

           Asphyxiation. Only the Sandia 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.
			  
			  Experts Generally Agreed That the Most Likely Public Safety Impact
			  of an LNG Spill Is Fireï¿½s Heat Effect, but That Further Study Is
			  Needed to Clarify the Extent of This Effect

           Our panel of 19 experts generally agreed on the public safety
           impact of an LNG spill and disagreed with a few of the conclusions
           of the Sandia study.^9 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.
			  
			  Experts Agreed That the Heat from an LNG Fire Was Most Likely to
			  Affect Public Safety, but That Explosions from an LNG Spill Are
			  Unlikely

           Experts discussed two types of fires: vapor cloud fires and pool
           fires. 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. While the initial vapor cloud fire
           would be of short duration as the flames burned back toward the
           LNG carrier, any flammable object enveloped by the vapor cloud
           fire could ignite nearby objects, creating secondary fires that
           present hazards to the public. Three experts emphasized in their
           comments that the vapor cloud is unlikely to penetrate very far
           into a populated area before igniting. Expanding on this point,
           one expert noted that any injuries from a vapor cloud fire would
           occur only at the edges of a populated area, for example, along
           beaches. One expert disagreed, arguing that a vapor cloud fire is
           unlikely to cause significant secondary fires because it would not
           last long enough to ignite other materials.

           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 and scenario-specific factors.
           Furthermore, a large, unconfined pool fire is very difficult to
           extinguish; generally almost all the LNG must be consumed before
           the fire goes out. Experts agreed that three of the main factors
           that affect the amount of heat from an LNG fire are the following:

           o Site-specific weather conditions. Weather conditions, such as
           wind and humidity, can influence the heat hazard distances. For
           example, more humid conditions allow heat to be absorbed by the
           moisture in the air, reducing heat hazard distances.
           o Composition of the LNG. The composition of the LNG can also
           affect the distance at which heat from the fire is felt by the
           public. In small fires, methane, which comprises between 84
           percent and 97 percent of LNG, burns cleanly, with little smoke.
           Other LNG components--propane and butane--produce more smoke when
           burned, absorbing some of the fire's heat and reducing the hazard
           distance. As the fire grows larger, the influence of the
           composition of LNG is hypothesized to be less pronounced because
           large fires do not burn efficiently.
           o Size of the fire. The size of the fire has a major impact on its
           surface emissive power; the heat hazard distance increases with
           pool size up to a point but is expected to decrease for very large
           pools, like those caused by a terrorist attack.

           Experts also discussed the following hazards related to an LNG
           spill:

           o RPTs. Experts agreed that RPTs could occur after an LNG spill
           but that the overpressures generated would be unlikely to directly
           affect the public.
           o Detonations and deflagrations. Experts made a key distinction
           between these types of explosions in confined spaces as opposed to
           unconfined spaces. For confined spaces, they agreed that it is
           possible, under controlled experimental conditions, to induce both
           types of explosions of LNG vapors; however, a detonation of
           confined LNG vapors is unlikely following an LNG spill caused by a
           terrorist attack. Experts were split on the likelihood of a
           confined deflagration occurring after a terrorist attack: eight
           thought it was unlikely, four thought it likely, and five thought
           neither likely nor unlikely.^10 For unconfined spaces, experts
           were split on whether it is possible to induce such explosions;
           however, even experts who thought such explosions were possible
           agreed that deflagrations and detonations in unconfined spaces are
           unlikely to occur following an LNG spill caused by a terrorist
           attack.

           o BLEVE. Experts were split on whether a BLEVE is theoretically
           possible in an LNG tanker. Of the ten experts who agreed it was
           theoretically possible, six thought that a BLEVE is unlikely to
           occur following an LNG spill caused by a terrorist attack on a
           tanker.^11 
           o Freeze burns and asphyxiation. Experts agreed that freeze burns
           do not present a hazard to the public because only people in close
           proximity to LNG spill, such as personnel on the tanker or nearby
           vessels, might come into contact with LNG or very cold LNG vapor.
           For asphyxiation, experts agreed that it is unlikely that an LNG
           vapor cloud could reach a populated area while still sufficiently
           concentrated to pose an asphyxiation threat.
			  
			  Experts Disagreed with a Few Key Conclusions of the Sandia
			  National Laboratories Study

           Experts disagreed with heat hazard and cascading failure
           conclusions of the Sandia study. Specifically, 7 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). Experts who thought the distance was too conservative
           generally listed one of two reasons. First, the assumptions about
           the surface emissive power of large fires were incorrect because
           the surface emissive power of large fires would be lower than
           Sandia assumed. Second, Sandia's hazard distances are based on the
           maximum size of a pool fire. However, these experts pointed out
           that once a pool fire ignites, its diameter will begin to shrink,
           which will also reduce the heat hazard distance. Experts who
           thought Sandia's heat hazard distance was not conservative enough
           listed a number of concerns. For example, Sandia's distances do
           not take into consideration the effects of cascading failure. One
           expert suggested that a 1-meter hole in the center tank of an LNG
           tanker that resulted in a pool fire could cause the near
           simultaneous failure of the other four tanks, leading to a larger
           heat hazard zone.

           Officials at Sandia National Laboratories and our panel of experts
           cautioned that the hazard distances presented cannot be applied to
           all sites. According to the Sandia study authors, their goal was
           to provide guidance to federal agencies on the order of magnitude
           of the hazards of an LNG spill on water. As they pointed out in
           interviews and in their original study, further analysis for
           specific sites is needed to understand hazards in a particular
           location. Six experts on our panel also emphasized the importance
           of site-specific and scenario-specific factors. For instance, one
           expert explained that the 5kW/m^2 hazard distance depends on the
           size of the tanker and the spill scenario, including factors such
           as wind speed, timing of ignition, and the location of the hole.
           Other experts suggested that key factors are spill volume and the
           impact of waves. 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."

           Only 9 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. Three experts said that an LNG
           spill and subsequent fire could potentially result in the loss of
           all tanks on board the tanker.

           Twelve of 16 experts agreed, however, with Sandia's conclusion
           that cascading failure events are not likely to greatly increase
           (by more than 20 to 30 percent) the overall fire size or heat
           hazard ranges. The four experts who disagreed with Sandia's
           conclusion about the public safety impact of cascading failure
           cited two main reasons: (1) Sandia did not clearly explain how it
           reached that conclusion and (2) the impact of cascading failure
           will partly depend on how the incident unfolds. For instance, one
           expert suggested that cascading failure could include a tank
           rupture, fireball, or BLEVE, any of which could have direct
           impacts on the public (from the explosive force) and which would
           change the heat hazard zones that Sandia identified.

           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.
			  
			  Experts Suggest Future Research Priorities to Determine the Public
			  Safety Impact of an LNG Spill

           In the second iteration of the Web-based panel, we asked the
           experts to identify the five areas related to the consequences of
           LNG spills that need further research. Then, in the final
           iteration of the Web-based panel, we provided the experts with a
           list of 19 areas--generated by their suggestions and comments from
           the second iteration--and asked them to rank these in order of
           importance. Table 2 presents the results of that ranking for the
           top 10 areas identified and indicates those areas that are funded
           in the DOE study discussed earlier.

           Table 2: Expert Panel's Ranking of Need for Research on LNG			  

                                                                   Funded in                                                                               
Rank Research area                                             DOE's study 
1    Large fire phenomena                                         X     
2    Cascading failure                                                     
3    Large-scale spill testing on water                           X     
4    Large-scale fire testing                                     X     
5    Comprehensive modeling: interaction of physical processes             
6    Risk tolerability assessments                                         
7    Vulnerability of containment systems (hole size)                      
8    Mitigation techniques                                                 
9    Effect of sea water coming in as LNG flows out                        
10   Impact of wind, weather, and waves          			  

           Source: GAO.

           Note: A rank of 1 is the highest rank, and a rank of 10 is the
           lowest. Panel members ranked 19 areas of research from 1 to 19; a
           score was calculated for each area based on this ranking. Only the
           10 areas with the highest scores are presented in this table.

           As the table shows, two of the top five research areas identified
           are related to large LNG fires--large fire phenomena and
           large-scale fire testing. Experts believe this research is needed
           to establish the relationship between large pool fires and the
           surface emissive power of the fire. Experts recommended new LNG
           tests for fires between 15 meters and 1,000 meters. The median
           suggested test size was 100 meters. Some experts also raised the
           issue of whether large LNG fires will stop behaving like one
           single flame but instead break up into several smaller, shorter
           flames. Sandia noted in its study that this behavior could reduce
           heat hazard distances by a factor of two to three.

           Experts also ranked research into cascading failure of LNG tanks
           second in the list of priorities. Concerning cascading failure,
           one expert noted that, although the consequences could be serious,
           there are virtually no data looking at the hull damage caused by
           exposure to extreme cold or heat.

           As table 2 shows, DOE's recently funded study involving
           large-scale LNG fire experiments addresses some, but not all, of
           the research priorities identified by the expert panel. For DOE,
           Sandia National Laboratories 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. The goal of this fire testing is to
           document the impact of smoke on large LNG pool fires. Sandia
           suggests that these tests will create a higher degree of knowledge
           of large-scale pool fire behavior and significantly lower the
           current uncertainty in predicting heat hazard distances.

           According to researchers at Sandia National Laboratories, some of
           the research our panel of experts suggested may not be
           appropriate. Sandia indicated that comprehensive modeling, which
           allows various complex processes to interact, would be very
           difficult to do because of the uncertainty surrounding each
           individual process of the model. One expert on our panel agreed,
           noting that while comprehensive modeling of all LNG phenomena is
           important, combining those phenomena into one model should wait
           for experiments that lead to better understanding of each
           individual phenomenon.
			  
^9We considered experts "in agreement" if more than 75 percent of experts
indicated that they completely agreed or generally agreed with a given
statement. Not all experts commented on every issue discussed.

^10Two experts did not comment.

^11Three experts said that BLEVEs were "neither likely nor unlikely," and
one expert thought that BLEVEs were likely.			  
			  
			  Conclusions

           It is likely that the United States will increasingly depend on
           the importation of LNG to meet the nation's demand for natural
           gas. Understanding and resolving the uncertainties surrounding LNG
           spills is critical, especially in deciding on where to locate LNG
           facilities. Because there have been no large-scale LNG spills or
           spill experiments, past studies have developed modeling
           assumptions based on small-scale spill data. While there is
           general agreement on the types of effects from an LNG spill, the
           results of these models have created what appears to be
           conflicting assessments of the specific consequences of an LNG
           spill, creating 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. Although DOE has recently funded a
           study that will address large-scale LNG fires, this study will
           address only 3 of the top 10 issues--and not the second-highest
           ranked issue--that our panel of experts identified as potentially
           affecting public safety.
			  
			  Recommendation for Executive Action

           To provide the most comprehensive and accurate information for
           assessing the public safety risks posed by tankers transiting to
           proposed LNG facilities, we recommend that the Secretary of Energy
           ensure that DOE incorporates the key issues identified by the
           expert panel into its current LNG study. We particularly recommend
           that DOE examine the potential for cascading failure of LNG tanks
           in order to understand the damage to the hull that could be caused
           by exposure to extreme cold or heat.
			  
			  Agency Comments and Our Evaluation

           We requested comments on a draft of this report from the Secretary
           of Energy (DOE). DOE agreed with our findings and recommendation.
           In addition, DOE included technical and clarifying comments, which
           we included in our report as appropriate.

           As agreed with your offices, unless you publicly announce the
           contents of this report earlier, we plan no further distribution
           until 30 days from the report date. At that time, we will send
           copies to interested congressional committees, the Secretary of
           Energy, and other interested parties. We also will make copies
           available to others upon request. In addition, the report will be
           available at no charge on the GAO Web site at http://
           www.gao.gov .

           If you or your staff have any questions regarding this report,
           please contact me at (202) 512-3841 or [email protected]. Contact
           points for our Offices of Congressional Relations and Public
           Affairs may be found on the last page of this report. Key
           contributors to this report are listed in appendix IV.

           Jim Wells
			  Director, Natural Resources and Environment
			  
			  Appendix I: Scope and Methodology

           To address the first objective, we identified eight unclassified,
           completed studies of liquefied natural gas (LNG) hazards and
           reviewed the six studies that included new, original research
           (either experimental or modeling) and clearly described the
           methodology used. While we have not verified the scientific
           modeling or results of these studies, the methods used seem
           appropriate for the work conducted based on conversations with
           experts in the field and our assessment. We also discussed these
           studies with their authors and visited all four onshore LNG import
           facilities and one export facility. We attended a presentation on
           LNG safety and received specific training on LNG properties and
           safety. We also conducted interviews with officials from Sandia
           National Laboratories, Federal Energy Regulatory Commission,
           Department of Transportation, Department of Energy, and the U. S.
           Coast Guard. During our interviews, we asked officials to provide
           information on past LNG studies and plans for future LNG spill
           consequences work.

           To obtain information on experts' opinions of the public safety
           consequences of an LNG spill from a tanker, we conducted a
           three-phase, Web-based survey of 19 experts on LNG spill
           consequences. We identified these experts from a list of 51
           individuals who had expertise in one or more key aspects of LNG
           spill consequence analysis. In compiling this initial list, we
           sought to achieve balance in terms of area of expertise (i.e., LNG
           experiments, modeling LNG dispersion, LNG vaporization, fire
           modeling, and explosion modeling). In addition, we included at
           least one author of each of the six major LNG studies we reviewed,
           that is, studies by Sandia National Laboratories; ABS Consulting;
           Quest Consultants Inc.; Pitblado, et al.; James Fay (MIT); and
           William Lehr (National Oceanic and Atmospheric Administration). We
           gathered resumes, publication lists, and major LNG-related
           publications from the experts identified on the initial list.

           We selected 19 individuals for the panel. One or more of the
           following selection criteria were used: (1) has broad experience
           in all facets of LNG spill consequence modeling (LNG spill from
           hole, LNG dispersion, vaporization and pool formation, vapor cloud
           modeling, fire modeling, and explosion modeling); (2) has
           conducted physical LNG experiments; or (3) has specific experience
           with areas of particular importance, such as LNG explosion
           research. In addition, we included: (1) at least one author from
           each of the major LNG studies and (2) representatives from private
           industry, consulting, academia, and government. All 19 experts
           selected for the panel agreed to participate. The names and
           affiliations of panel members are included in appendix II.

           To obtain consensus concerning public safety issues, we used an
           iterative Web-based process. We used this method, in part, to
           eliminate the potential bias associated with group discussions.
           These biasing effects include the potential dominance of
           individuals and group pressure for conformity. Moreover, by
           creating a virtual panel, we were able to include more experts
           than possible with a live panel.

           For each phase in the process, we posted a questionnaire on GAO's
           survey Web site. Panel members were notified of the availability
           of the questionnaire with an e-mail message. The e-mail message
           contained a unique user name and password that allowed each
           respondent to log on and fill out a questionnaire but did not
           allow respondents access to the questionnaires of others.

           In the questionnaires, we asked the experts to agree or disagree
           with a set of statements about LNG hazards derived from GAO's
           synthesis of major LNG spill consequence studies. Prior to the
           first iteration, we had an LNG spill consequence expert who was
           not a part of the panel review each statement and provide comments
           about technical accuracy and tone. Experts were asked to indicate
           agreement on a 3-point scale (completely agree, generally agree,
           do not agree) and to provide comments about how the statements
           could be changed to better reflect their understanding of the
           consequences of LNG spills.

           If most experts agreed with a statement during the first
           iteration, we did not include it in the second iteration. If there
           was not agreement, we used the experts' comments to revise the
           statements for the second iteration. The second iteration was
           posted on the Web site, using the same protocol as used for the
           first. Again, panel members were asked to agree or disagree and
           provide narrative comments. We revised the statements where there
           was disagreement and posted them on the Web site again for the
           third iteration. At the end of the third iteration, at least 75
           percent of the experts agreed or generally agreed with most of the
           ideas presented.

           Because some of the studies conducted are classified, this public
           version of our findings supplements a more comprehensive
           classified report produced under separate cover. We conducted our
           work from January 2006 through January 2007 in accordance with
           generally accepted government auditing standards.
			  
			  Appendix II: Names and Affiliations of Members of GAOï¿½s Expert
			  Panel on LNG Hazards

Myron Casada   ABS Consulting                                  
T.Y. Chu       Sandia National Laboratories                    
Philip Cleaver Advantica                                       
Bob Corbin     U.S. Department of Energy                       
John Cornwell  Quest Consultants, Inc.                         
James Fay      Massachusetts Institute of Technology           
Louis Gritzo   FM Global                                       
Jerry Havens   University of Arkansas                          
Benedict Ho    BP                                              
Greg Jackson   University of Maryland                          
Ron Koopman    Hazard Analysis Consulting                      
Bill Lehr      National Oceanic and Atmospheric Administration 
Georges Melhem ioMosaic Corporation                            
Gordon Milne   Lloyd's Register                                
Robin Pitblado Det Norske Veritas                              
Phani Raj      Technology and Management Systems, Inc.         
Velisa Vesovic Imperial College                                
Harry West     Texas A&M University                            
John Woodward  Baker Engineering and Risk Consultants, Inc.    			  
			  
			  Appendix III: Summary of Expert Panel Results

           For each question below, we show only those responses that were
           selected by at least one expert. The number of responses adds up
           to 19--the total number of experts on the panel. Percentages may
           not add to 100% due to rounding.
			  
			  Introduction

           Large LNG spills from a vessel could be caused by an accident,
           such as collision or grounding, or by an intentional attack. While
           large accidental LNG spills are highly unlikely given current LNG
           carrier designs and operational safety policies and practices,
           these spills do pose a hazard to the public if they occur in or
           near a populated area. What is your level of agreement with this
           paragraph? (Finalized in the second iteration.)
			  
Count Percentage  Label            
8         42.11%  Completely agree 
11        57.89%  Generally agree  
			  
			  LNG Hazards
			  
			  Overall Hazards

           LNG is a cryogenic liquid composed primarily of methane with low
           concentrations of heavier hydrocarbons, such as ethane, propane,
           and butane. LNG is colorless, odorless, and nontoxic. When LNG is
           spilled, it boils and forms LNG vapor (natural gas). The LNG vapor
           is initially denser than ambient air and visible; LNG vapor will
           stay close to the surface as it mixes with air and disperses. LNG
           and LNG vapor pose four possible hazards: freeze burns,
           asphyxiation, fire hazard, and explosions. What is your level of
           agreement with this paragraph? (Finalized in the second
           iteration.)
			  
Count Percentage  Label            
5         26.32%  Completely agree 
12        63.16%  Generally agree  
2         10.53%  Do not agree 		  
			  
			  LNG Hazards-Freeze Burns

           LNG poses a threat of freeze burns to people who come into contact
           with the liquid or with very cold LNG vapor. Since LNG boils
           immediately and vaporizes after it leaves an LNG tank and LNG
           vapor warms as it mixes with air, only people in close proximity
           to the release, such as personnel on the tanker or nearby escort
           vessels, might come into contact with LNG or LNG vapor while it is
           still cold enough to result in freeze burns. Freeze burns do not
           present a direct hazard to the public. What is your level of
           agreement with this paragraph? (Finalized in the second
           iteration.)
			  
Count Percentage  Label            
14        73.68%  Completely agree 
5         26.32%  Generally agree  
			  
			  LNG Hazards-Asphyxiation

           After an LNG spill, LNG vapor forms a dense, visible vapor cloud
           that is initially heavier than air and remains close to the
           surface. The cloud warms as it mixes with air and as portions of
           the cloud reach ambient air temperatures, they begin to rise and
           disperse. Asphyxiation occurs when LNG vapor displaces oxygen in
           the air. Asphyxiation is a threat primarily to personnel on the
           LNG tanker or to people aboard vessels escorting the tanker at
           close range. An LNG vapor cloud could move away from the tanker as
           it mixes with air and begins to disperse. However, it is unlikely
           that the vapor cloud could reach a populated area while still
           sufficiently concentrated to pose an asphyxiation threat to the
           public. What is your level of agreement with this paragraph?
           (Finalized in the second iteration.)
			  
Count Percentage  Label            
8         42.11%  Completely agree 
10        52.63%  Generally agree  
1          5.26%  Do not agree     
			  
			  LNG Hazards-Vapor Cloud: Wind Effect

           The effect of wind on an LNG vapor cloud varies with wind speed.
           The most hazardous wind conditions, however, are low winds, which
           can push a vapor cloud downwind without accelerating the LNG vapor
           dispersion into the atmosphere. Low wind conditions have the
           highest potential of allowing an LNG vapor cloud to move a
           significant distance downwind. What is your level of agreement
           with this paragraph? (Finalized in the third iteration.)
			  
Count Percentage  Label            
8         42.11%  Completely agree 
10        52.63%  Generally agree  
1          5.26%  Do not agree     
			  
			  LNG Hazards-Fire Hazard

           Because LNG vapor in an approximately 5 to 15 percent mixture with
           air is flammable, LNG vapor within this flammability range is
           likely to ignite if it encounters a sufficiently strong ignition
           source such as a cigarette lighter or strong static charge. What
           is your level of agreement with this paragraph? (Finalized in the
           third iteration.)
			  
Count Percentage  Label            
13        68.42%  Completely agree 
6         31.58%  Generally agree  
			  
			  LNG Hazards-Fire Hazard: Thermal Hazard End Point

           The main hazard to the public from a pool fire is the thermal
           radiation, or heat, that is generated by the fire rather than the
           flames themselves. Often this heat is felt at considerable
           distance from the fire. Scientific papers have used two different
           thresholds as end points to describe the impact of thermal
           radiation on the public: 5 kilowatts per square meter and 1.6
           kilowatts per square meter. Which level do you think is the
           appropriate end point to use to define thermal hazard zones in
           order to protect the public? (Please indicate your response, then
           provide an explanation in the textbox below your answer.)
			  
Count Percentage  Label                                                    
8         42.11%  5 kilowatts per square meter                             
2         10.53%  1.6 kilowatts per square meter                           
6         31.58%  Other                                                    
3         15.79%  I do not have the expertise necessary to respond to this 
                     question.                                                

           Of the six experts who answered "other," two experts indicated
           that 5kW/m^2 is a useful or appropriate level for measuring the
           impact on people. One expert suggested that dosage (a measure that
           combines thermal radiation and duration of exposure) is most
           appropriate. Another expert suggested that both thresholds are
           appropriate, depending on the circumstances of the analysis.
           (Finalized in the first iteration.)
			  
			  LNG Hazards-Fire Hazard: Pool Fire

           A pool fire could form in the wake of a vapor cloud fire burning
           back to the source or just after an LNG spill, if there is
           immediate ignition of the LNG vapor. A pool fire burns the vapor
           above a liquid LNG pool as the liquid boils from the pool. A
           large, unconfined pool fire is very difficult to extinguish;
           generally almost all the LNG must be consumed before the fire goes
           out. What is your level of agreement with this paragraph?
           (Finalized in the second iteration.)
			  
Count Percentage  Label            
13        68.42%  Completely agree 
5         26.32%  Generally agree  
1          5.26%  Do not agree     

           The main hazard to the public from a pool fire is the thermal
           radiation, or heat, from the fire. This heat can be felt at a
           considerable distance from the flames themselves. Numerous factors
           can impact the amount of thermal radiation that could affect the
           public: site-specific weather conditions, including humidity and
           wind speed and direction, the composition of the LNG, and the size
           of the fire. What is your level of agreement with this paragraph?
           (Finalized in the second iteration.)
			  
Count Percentage  Label            
13        68.42%  Completely agree 
6         31.58%  Generally agree  

           The wind speed and direction also affect the distance at which
           thermal radiation from the fire is felt by the public. In high
           winds, the flames will tilt downwind, increasing the amount of
           heat felt downwind of the fire and decreasing the amount of heat
           felt upwind. More humid conditions allow heat to be absorbed by
           the moisture in the air reducing the heat felt by the public. What
           is your level of agreement with the above paragraph? (Finalized in
           the second iteration.)
			  
Count Percentage  Label                                                    
6         31.58%  Completely agree                                         
11        57.89%  Generally agree but suggest the following clarification. 
2         10.53%  I do not have the expertise necessary to respond to this 
                     section.                                                 

           The composition of the LNG can also affect the distance at which
           thermal radiation from the fire is felt by the public. In small
           fires, methane, which comprises between 84 percent and 97 percent
           of LNG, burns cleanly, with little smoke. Cleaner-burning LNG
           fires, particularly those burning LNG with higher methane content,
           result in higher levels of thermal radiation than oil or gasoline
           fires of the same size because the smoke generated by oil and
           gasoline fires acts as a shield, reducing the amount of thermal
           radiation emitted by the fire. While LNG composition can have a
           large impact on the thermal radiation from small LNG fires, as LNG
           fires get larger, these effects are hypothesized to be less
           pronounced. What is your level of agreement with this paragraph?
           (Finalized in the third iteration.)
	
Count Percentage  Label                                                    
5         26.32%  Completely agree                                         
10        52.63%  Generally agree                                          
3         15.79%  Do not agree                                             
1          5.26%  I do not have the expertise necessary to respond to this 
                     section.       			  

           The size of the fire has a major impact on the thermal radiation
           from an LNG pool fire. Thermal radiation increases with pool size
           up to a point but is expected to decrease for very large pools,
           like those caused by a terrorist attack. What is your level of
           agreement with this paragraph? (Finalized in the second
           iteration.)

Count Percentage  Label                                                    
4         21.05%  Completely agree                                         
10        52.63%  Generally agree                                          
4         21.05%  Do not agree                                             
1          5.26%  I do not have the expertise necessary to respond to this 
                     section.                                                 
			  
			  LNG Hazardsï¿½Vapor Cloud Fire

           If an LNG vapor cloud formed in the wake of an LNG spill and
           drifted away from the tanker as it warmed and dispersed, the vapor
           cloud could enter a populated area while areas of the cloud had
           LNG vapor/air mixtures within the flammability range. Since
           populated areas have numerous ignition sources, those portions of
           the cloud would likely ignite. The fire would then burn back
           through the cloud toward the tanker and continue to burn as a pool
           fire near the ship, assuming that liquid LNG still remains in the
           spill area. Ignition of a vapor cloud over a populated area could
           burn people and property in the immediate vicinity of the fire.
           While the initial fire would be of short duration as the flames
           burned back toward the LNG carrier, secondary fires could continue
           to present a hazard to the public. What is your level of agreement
           with the above paragraph? (Finalized in the second iteration.)
			  
Count Percentage  Label                                                   
7         36.84%  Completely agree                                        
11        57.89%  Generally agree but suggest the following clarification 
1          5.26%  Do not agree                                            

           LNG Hazardsï¿½Vapor Cloud Fire: Burn Back Speed

           After ignition of a vapor cloud that drifted away from an LNG
           tanker spill, how fast could the flame front travel back toward
           the spill site if it was unconfined or confined? (Finalized in the
           second iteration.)
			  
Count Percentage  Label                                                    
15        78.95%  Not checked                                              
2         10.53%  I do not have the expertise necessary to respond to this 
                     section.                                                 
2         10.53%  No answer                                                

           Experts did not agree on the speed of a flame front traveling
           through an LNG vapor cloud in either a confined or unconfined
           state. Responses varied from less than 5 meters per second up to
           50 meters per second in unconfined settings and from 0 meters per
           second to 2,000 meters per second in confined settings.
			  
			  Explosions-RPT

           A rapid phase transition (RPT) can occur when LNG spilled onto
           water changes from liquid to gas virtually instantaneously due to
           the rapid absorption of ambient environmental heat. While the
           rapid expansion from a liquid to vapor state can cause locally
           large overpressures, an RPT does not involve combustion. RPTs have
           been observed during LNG test spills onto water. In some cases,
           the overpressures generated were strong enough to damage test
           equipment in the immediate vicinity. Overpressures generated from
           RPTs would be very unlikely to have a direct affect on the public.
           What is your level of agreement with this paragraph? (Finalized in
           the second iteration.)
			  
Count Percentage  Label            
15        78.95%  Completely agree 
4         21.05%  Generally agree  

			  
			  Explosions-Deflagrations and Detonations

           Deflagrations and detonations are rapid combustion processes that
           move through an unburned fuel-air mixture. Deflagrations move at
           subsonic velocities and can result in overpressures up to eight
           times the original pressure, particularly in congested/confined
           areas. Detonations move at supersonic velocities and can result in
           overpressures up to 20 times the original pressure. What is your
           level of agreement with this paragraph? (Finalized in the third
           iteration.)
			  
Count Percentage  Label            
1          5.26%  Not checked      
7         36.84%  Completely agree 
10        52.63%  Generally agree  
1          5.26%  Do not agree     			  
			  
			  Explosionsï¿½Deflagrations, Detonations, and BLEVEs

           Please choose the response that best describes your opinion about
           each type of explosion of LNG vapors in each setting described.
           (Finalized in the third iteration.)

             Deflagration Deflagration                                                                
                     with         with                                                                
             overpressure overpressure Detonation Detonation                                          
                    in an         in a      in an       in a                                          
               unconfined     confined unconfined   confined Boiling-liquid-expanding-vapor-explosion 
Answer            setting      setting    setting    setting                                  (BLEVE) 
Under                                                                                                 
controlled                                                                                            
experimental                                                                                          
conditions,                                                                                           
it is                                                                                                 
possible to                                                                                           
induce this                                                                                           
type of                                                                                               
explosion in                                                                                          
this type of                                                                                          
setting.                7           18          4         15                                       11 
This type of                                                                                          
setting                                                                                               
cannot                                                                                                
support this                                                                                          
type of                                                                                               
explosion.              8            0         11          2                                        7 
More                                                                                                  
research is                                                                                           
necessary to                                                                                          
answer this                                                                                           
question.               3            0          3          0                                        0 
I don't have                                                                                          
the                                                                                                   
expertise                                                                                             
necessary to                                                                                          
answer this                                                                                           
question.               0            0          0          1                                        0 
No                                                                                                    
answer/not                                                                                            
checked                 1            1          1          1                                        1 

           If experts answered that "under controlled experimental
           conditions, it is possible to induce this type of explosion in
           this type of setting," they were asked to answer the following
           question:

           What is the likelihood of a each type of explosion of LNG vapors
           in each setting described occurring following an LNG spill caused
           by a terrorist attack on a tanker? (Finalized in the third
           iteration.)
			  
         Deflagration Deflagration                                                                
                 with         with                                                                
         overpressure overpressure Detonation Detonation                                          
                in an         in a      in an       in a                                          
           unconfined     confined unconfined   confined Boiling-liquid-expanding-vapor-explosion 
Answer        setting      setting    setting    setting                                  (BLEVE) 
Highly              3            6          1          7                                        4 
unlikely                                                                                          
Unlikely            2            2          3          3                                        2 
Neither             1            5          0          3                                        3 
likely                                                                                            
nor                                                                                               
unlikely                                                                                          
Likely              1            4          0          2                                        1 
Highly              0            0          0          0                                        0 
likely                                                                                            
No                  0            1          0          0                                        1 
answer/                                                                                           
not                                                                                               
checked                                                                                           
			  
			  LNG Hazardsï¿½Is BLEVE the Worst?

           A BLEVE is the worst potential hazard of an LNG spill. It would
           result in the rupture of one or more LNG tanks, perhaps
           simultaneously, on the ship, with potential rocketing debris and
           damaging pressure waves. What is your level of agreement with the
           above paragraph? (Finalized in the first iteration.)
			  
Count Percentage  Label                                               
2         10.53%  Completely agree                                    
16        84.21%  Do not agree (Please explain in the textbox below.) 
1          5.26%  No answer                                           
			  
			  Questions About the 2004 Sandia National Laboratories Study1

           The Sandia report concluded that the most significant impacts to
           public safety exist within 500 meters of a spill, with much lower
           impacts at distances beyond 1,600 meters even for very large
           spills. Please choose the response that best describes your
           opinion about these hazard distances. (Finalized in the third
           iteration.)
			  
Count Percentage  Label                                                    
4         23.54%  They are too conservative (i.e., should be smaller)      
7         41.18%  They are about right                                     
4         23.53%  They are not conservative enough (i.e., should be        
                     larger)                                                  
2         11.76%  No answer                                                
			  
1Since two of the experts were authors of the Sandia study, their
responses to ALL the questions related to the study below have been
excluded. For the questions related to the Sandia study, there are 17
experts responding.

           The Sandia report concluded that large, unignited LNG vapor clouds
           could spread over distances greater than 1,600 meters from a
           spill. For a nominal intentional spill, the hazard range could
           extend to 2,500 meters. The actual hazard distances will depend on
           breach and spill size, site-specific conditions, and environmental
           conditions. Please choose the response that best describes your
           opinion about these hazard distances. (Finalized in the third
           iteration.)
			  
Count Percentage  Label                                                    
4         23.53%  They are too conservative (i.e., should be smaller)      
6         35.29%  They are about right                                     
4         23.53%  They are not conservative enough (i.e., should be        
                     larger)                                                  
1          5.88%  Do not have the expertise to answer                      
2         11.76%  No answer                                                

           The Sandia report concluded that cascading damage (multiple cargo
           tank failure) due to brittle fracture from exposure to cryogenic
           liquid or fire-induced damage to foam insulation is possible under
           certain conditions but is not likely to involve more than two or
           three cargo tanks for any single incident. What is your level of
           agreement with this paragraph? (Finalized in the third iteration.)
			  
Count Percentage  Label                                                    
3         17.65%  Completely agree                                         
6         35.29%  Generally agree                                          
6         35.29%  Do not agree                                             
2         11.76%  I do not have the expertise necessary to respond to this 
                     section.                                                 

           The Sandia report concluded that cascading events are not expected
           to greatly increase (not more than 20-30 percent) the overall fire
           size or hazard ranges (500 meters for severe impacts, much lower
           impacts beyond 1,600 meters) but will increase the expected fire
           duration. What is your level of agreement with this paragraph?
           (Finalized in the third iteration.)

           The Sandia report suggested that consequence studies should be
           used to support comprehensive, risk-based management and planning
           approaches for identifying, preventing, and mitigating hazards to
           public safety and property from potential LNG spills. What is your
           level of agreement with this paragraph? (Finalized in the third
           iteration.)
			  
			  Commodity Comparison

           In your opinion, what is the risk to public safety posed by an
           attack on tankers carrying each of the following energy
           commodities? (Finalized in the first iteration.)

                  Liquefied Crude                 Heating  Jet      Liquefied 
Answer       natural gas   oil Diesel Gasoline     oil fuel  petroleum gas 
Little to                                                                  
None                   1     2      1        0       1    1              0 
Little                 3    10     11        5      11    6              1 
Medium                 6     3      3        8       3    6              4 
Large                  3     0      0        2       0    2              5 
Very Large             2     0      0        0       0    0              5 
No expertise                                                               
to answer              1     1      1        1       1    1              1 
No answer              3     3      3        3       3    3              3 			  
			  
			  Future Research

           In the first and second survey iterations, you noted areas related
           to LNG spill consequences that need further research. We are
           interested in your thoughts on the relative level of need for
           research in these areas, and also the five areas you think should
           be of highest priority in future research.

           Please indicate the degree to which further research is needed in
           each of the areas listed below. (Finalized in the third
           iteration.)

           Responses to each part of this question are in the table below,
           which is sorted by mean score so that the highest-ranked research
           priorities appear first.

                                                             Do not              
                          Very                     Little  have the              
                         great Great          Some  to no expertise     No       
                          need  need Moderate need   need to answer answer  Mean 
 Type of research          (1)   (2)  need(3)  (4)    (5)       (6)    (7) score 
 Large fire phenomena                                                            
 (impact of smoke                                                                
 shielding, large flame                                                          
 versus smaller                                                                  
 flamelets)                  9     5        3    0      1         1      0  4.17 
 Cascading failure           5     9        4    1      0         0      0  3.95 
 Large-scale LNG spill                                                           
 testing on water^a          7     7        2    1      2         0      0  3.84 
 Large-scale fire                                                                
 testing^b                   7     6        3    2      1         0      0  3.84 
 Comprehensive modeling                                                          
 allowing different                                                              
 physical processes to                                                           
 interact                    2    10        3    4      0         0      0  3.53 
 Risk tolerability                                                               
 assessments                 5     4        3    1      3         1      2  3.44 
 Vulnerability of LNG                                                            
 containment systems,                                                            
 including validating                                                            
 hole size predictions                                                           
 for the double hull                                                             
 ship structure              5     4        3    5      2         0      0  3.26 
 Mitigation techniques       3     5        6    3      2         0      0  3.21 
 Effect of sea water                                                             
 pouring into a hole as                                                          
 LNG flows out               2     6        5    3      2         0      1  3.17 
 Impact of wind,                                                                 
 weather, and waves (on                                                          
 pool spread size,                                                               
 evaporation rate, pool                                                          
 formation, etc.)            3     4        6    3      3         0      0  3.05 
 Improvements to 3-D                                                             
 computational fluid                                                             
 dynamics dispersion                                                             
 modeling                    0     4        6    6      2         1      0  2.67 
 Effects of different                                                            
 LNG compositions (on                                                            
 vaporization rates,                                                             
 thermal radiation,                                                              
 explosive behavior,                                                             
 etc.)                       2     2        4    8      3         0      0  2.58 
 Whether an explosive                                                            
 attack will result in                                                           
 immediate vapor cloud                                                           
 ignition                    0     5        4    5      4         1      0  2.56 
 Rapid phase                                                                     
 transitions: likelihood                                                         
 in various scenarios                                                            
 and impact                  1     2        6    6      4         0      0  2.47 
 Effects of igniting LNG                                                         
 vapors in containment                                                           
 or ballast tanks            0     5        3    5      6         0      0  2.37 
 BLEVE properties of                                                             
 tanks on LNG ships          1     4        3    4      7         0      0  2.37 
 Deflagration/detonation                                                         
 of LNG                      1     0        5    8      5         0      0  2.16 
 Effects of a large,                                                             
 unignited vapor cloud                                                           
 drifting from the                                                               
 incident site               0     0        7    5      7         0      0  2.00 
 Effect of clothing and                                                          
 obstructions on the                                                             
 radiant heat level                                                              
 received by the public      1     1        2    6      9         0      0  1.89 
 Other^c                    12     2        0    0      0         0      5     d 

           aExperts suggested pool sizes of 15 meters up to 1,000 meters,
           though the median response was 100 meters.

           bExperts suggested pool sizes of 15 meters up to 1,000 meters,
           though the median response was 100 meters.

           cExperts suggested frequency modeling, determination of acceptable
           risk to society, analysis of foam on LNG tankers, risk analysis
           for larger LNG tankers, CFD modeling for pool spreading and
           evaporation, and improvement to existing techniques used for
           fighting LNG fires.

           dNot applicable.
			  
			  Appendix IV: GAO Contact and Staff Acknowledgments
			  
			  GAO Contact

           Jim Wells, (202) 512-3841, or [email protected]
			  
			  Staff Acknowledgments

           In addition to the individual named above, Mark Gaffigan, Amy
           Higgins, Lynn Musser, Janice Poling, Rebecca Shea, Carol
           Herrnstadt Shulman, and James W. Turkett made key contributions to
           this report.
			  
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www.gao.gov/cgi-bin/getrpt?GAO-07-316 .

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
[email protected].

Highlights of [48]GAO-07-316 , a report to congressional requesters

February 2007

MARITIME SECURITY

Public Safety Consequences of a Terrorist Attack on a Tanker Carrying
Liquefied Natural Gas Need Clarification

The United States imports natural gas by pipeline from Canada and by
tanker as liquefied natural gas (LNG) from overseas. LNG--a supercooled
form of natural gas--currently accounts for about 3 percent of total U.S.
natural gas supply, with an expected increase to about 17 percent by 2030,
according to the Department of Energy (DOE). With this projected increase,
many more LNG import terminals have been proposed. However, concerns have
been raised about whether LNG tankers could become terrorist targets,
causing the LNG cargo to spill and catch on fire, and potentially explode.
DOE has recently funded a study to consider these effects; completion is
expected in 2008.

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 concerning the consequences of a terrorist
attack on an LNG tanker. To address these objectives, GAO, among other
things, convened an expert panel to discuss the consequences of an attack
on an LNG tanker.

[49]What GAO Recommends

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 our draft report, DOE agreed with our recommendation.

The six unclassified completed studies GAO reviewed examined the effect of
a fire resulting from an LNG spill but produced varying results; some
studies also examined other potential hazards of a large LNG spill. 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
researchers had to make modeling assumptions since there are no data for
large LNG spills, either from accidental spills or spill experiments.
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.
DOE's recently funded study involving large-scale LNG fire experiments
addresses some, but not all, of the research priorities identified by the
expert panel. The leading unaddressed priority the panel cited was the
potential for cascading failure of LNG tanks.

LNG Tanker Passing Downtown Boston on Its Way to Port

References

Visible links
  48. http://www.gao.gov/cgi-bin/getrpt?GAO-07-316
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