Spills and Fires
from LNG Tankers in
Fall River (MA)
By Professor James A. Fay,
Massachusetts Institute of Technology
August 26, 2003
The events of September
11, 2001 have raised concerns about the potential for terrorists
attacks on the energy system infrastructure of the United States.
In particular, the possibility of the use of a boat bomb, such
as was used against the USS Cole in 2000 and the oil tanker Limburg
in 2002, to attack a marine liquid fuel tanker in a U.S. harbor,
was publicly discussed in Massachusetts, where both LNG (liquefied
natural gas) and oil product tankers land cargoes in Boston harbor.
The consequences of such an incident could be severe, and present
a potential problem of great magnitude for public safety officials.
The safety concerns
for the public stem from the effects of the burning of the tanker's
combustible liquid cargo, which would certainly escape from cargo
holds punctured by the force of an explosion. The ensuing fire
can spread on the sea surface toward nearby shorelines, and its
thermal radiation could produce bodily harm to exposed individuals
on shore and possibly set fire to shoreside buildings.
The fire that would
ensue from a boat bomb attack on a tanker would be of unprecedented
size and intensity. Like the attack on the World Trade Center
in New York City, there exists no relevant industrial experience
with fires of this scale from which to project measures for securing
public safety. Lacking such experience, we must rely on scientific
understanding to predict their characteristics, based upon laboratory
and field experiments of much smaller fires.
The author has developed
a mathematical model for the spills and fires from liquefied
fuel marine tankers which is based upon published scientific
papers in peer-reviewed journals (Fay,
Model of Spills and Fires from LNG and Oil Tankers,
Journal of Hazardous Materials, B96, 171-188, 2003). The purpose of this article
is to apply this research to the case of Fall River (MA) harbor.
Weaver's Cove Energy
LLC has proposed to construct and operate a marine LNG import
terminal on the Taunton River in Fall River (MA) (Weaver's Cove Energy LLC, Weaver's
Cove Energy LNG Import Terminal, Fall River, June 30, 2003).
To reach this terminal,
ocean-going LNG tankers must move through Narragansett and Mount
Hope Bays and enter the Taunton River, passing within 1000 feet
of downtown Fall River waterfront and near commercial and residential
areas. A tanker spill fire at any location along this route would
have serious consequences for persons and property on the shore
adjacent to the stricken vessel.
LNG Tanker Spills
The liquid fuel carried
in sea-going LNG tankers is stored in separate holds, each of
which may be as large as 25,000 cubic meters holding 10,500 tons
of cargo. A powerful explosion close along side the tanker can
puncture at least one hold and allow the cargo to drain out upon
the surrounding sea surface. The upper part of the cargo fluid
that is higher than the sea surface level will first leak out,
but additional cargo may also be ejected. Given an explosively
formed hole of sufficient size, such cargoes can be disgorged
LNG is lighter than
sea water. Once spilled, it floats, unmixed, on the sea surface.
Most importantly, it speedily spread sideways, exposing the fuel
to the air above. Once ignited, as is very likely when the spill
is initiated by a chemical explosion, the floating LNG pool will
burn vigorously. The time to burn spills of the size mentioned
above can be less than five minutes.
Fires that burn thousands
of tons of fuel in a few minutes are extraordinarily large, lying
well outside the range of domestic firefighting experience. Such
fires can be damaging to people and can set afire combustible
Maximum Pool Size
and Fire Duration:
To illustrate the characteristics
of such spills in Fall River harbor, we consider a typical spill
of LNG. (The relevant spill parameters are listed in Table 1.)
The LNG spill volume is 14,300 cubic meters or 3.8 million gallons.
Provided the vessel hole area is greater than ten square meters,
the maximum pool fire area is 180,000 square meters (44 acres)
and radius is 340 meters (1115 feet), while the fire duration
is 3.3 minutes.
1: Physical parameters
of a typical LNG tanker spill
||14,300 cubic meters
= 3.8 million gal.
|| 3.3 minutes
|Maximum pool area
square meters = 44 acres
|Maximum pool radius
|| 340 meters
= 1115 feet
|Average heat release
|Distance to average
heat flux of 5 kilowatts per square meter
|| 1100 meters
= 3600 feet
The pool fire, initiated
at the time of the explosion, grows in area in proportion to
the time since initiation, reaching maximum extent at the end
of the burning process. Maximum pool size for an LNG spill located
at the proposed LNG terminal: the outer edge of pool fire extends
to both east and west shores of the Taunton River. For a spill
anywhere along the path of an LNG tanker approaching the terminal,
the pool fire would reach Fall River shore. It is most certain
that combustible buildings long the waterfront would be ignited
by contact with the pool fire.
The extent of the pool
fires, which spread to distances greater than the ship length
in a short time, would make it impossible to move the stricken
vessel away from the waterfront areas. The potential for retarding
the pool spread is nonexistent.
Pool Fire Thermal
Burning LNG emits thermal
radiation that, if intense enough, can cause skin burns on humans
exposed to the radiation and can ignite combustible materials
on buildings. The more intense the radiation, the shorter is
the exposure time needed to cause a skin burn or combustible
For human skin exposure
to flame thermal radiation, a thermal flux of 5 kilowatts per
square meter will result in unbearable pain after an exposure
of 13 seconds and second degree burns after an exposure of 40
seconds. Exposure to twice that level, 10 kilowatts per square
meter, for 40 seconds is the threshold for fatalities (K.S.Mudan, Thermal radiation
hazards from hydrocarbon pool fires, Progress in Energy Combustion
Science, 10, 59-80, 1984).
Wood can be ignited after 40 seconds exposure at a thermal flux
of 5 kilowatts per square meter.
We have chosen a thermal
flux of 5 kilowatts per square meter a a criterion for the limit
for significant damage to humans and combustible materials and
have calculated the distance from the spill site at which that
flux would be experienced (These
distances are based upon an analysis contained in Fay, Model
of large pool fires, submitted to the Journal of Hazardous
Materials). As listed
in Table 1, this distance is 1100 meters (3600 feet or 0.68 mile)
for an LNG spill.
For an LNG spill, the
thermal radiation damage zone encloses 940 acres, including about
400 acres of land area in Fall River. Within this zone, extending
3600 feet from a spill site in the main channel of the Taunton
River, skin burns to humans exposed for only a fraction of a
minute will occur, and building fires can be induced. Beyond
the shorefront, at 1600 feet from the spill site, where the thermal
radiation flux is 10 kilowatts per square meter, fatalities can
One cannot exaggerate
the thermal intensity of the LNG pool fire. It's average heat
release rate is about twice the average thermal power consumption
of all U.S. fossil fuel electric power plants.
The analysis summarized
in this report, based upon studies published in peer-reviewed
scientific journals, sets forth the physical characteristics
of the fires to be expected from a boat bomb attack on an LNG
tanker in Fall River harbor. The major conclusions are:
- The magnitude of the
resulting liquid cargo pool fires are unprecedented in scale.
There is no possibility of ameliorating the fire's effects, much
less extinguishing it, during the short time (several minutes)
- At any point along
the inner harbor route of ship travel from sea to berth, pool
fire thermal radiation that can burn and even kill exposed humans,
and ignite combustible buildings, will be experienced along and
well inland from the waterfront.