Report - Agence canadienne d'évaluation environnementale

Assessing the risks related to the project
In his analysis, the proponent took into account incidents which could lead to LNG spills
during the transit of LNG tankers. To that end, the consequences of accident scenarios
deemed to be most likely were considered. According to the analysis, the ship’s outer hull
would not be breached in the case of a grounding, and even less so for the inner hull, in
view of river’s sandy bed and the security margin ensured through the proper design and
manufacture of the ship hulls and tanks. LNG tankers could therefore face the vagaries of
the tides without impact on the inside tanks (Mr. Glenn Kelly, DT3, p. 26 and 27).
A study was conducted in this respect by the Bureau Veritas to assess the resistance
of ship structures and the integrity of cargo containment systems when dealing with
tides having an amplitude of 6 m. The study concluded that the cases of grounding
studied pointed to a significant security margin with respect to the risk of major
damage to the structure or damages done to the cargo containment system, including
for several tidal cycles (DA13). Moreover, in the event of a spill resulting from this type
of accident, then the probability of spontaneous combustion was estimated at
10 percent by the proponent, as the breach would occur underwater.
According to the proponent, only an accident occurring close to the terminal could
result in a cloud of gas that could spread over a great distance and reach an area of
medium population density. In the event of a collision occurring in the seaway, the
probability of instantaneous combustion was estimated at 90 percent, as a major
collision would generate sufficient force to create sparks.
Both the proponent and Transport Canada agreed that certain conditions would be required
to actually breach the inner tank. These include a speed of eight knots or more for a ship of
50,000 t or more, at 90 o on the side of the LNG tanker (Mr. Glenn Kelly, DT6, p. 86).
In this respect, the Panel notes that the Sandia National Laboratories report also
specified that these same conditions would have to be brought together to breach the
inner hull of an LNG tanker (Sandia, 2004, p. 100 1 ).
Furthermore, the proponent estimated at 50 percent the probability of a delayed cloud
ignition in an inhabited area after a collision or grounding.
During the hearing, many participants expressed doubts regarding LNG tankers ability
to safely navigate the St. Lawrence River. Several participants were concerned that
an LNG tanker could become grounded in the Traverse du Nord or even in front of île
d’Orléans. In this respect, the proponent stated that “even in the worst grounding case
scenario, there are techniques which, firstly, allow the ships to float free and secondly,
let other ships safely pass by” (Mr. Glenn Kelly, DT6, p. 85).
1. Op. cit.
132 Rabaska Project – Implementation of an LNG Terminal and Related Infrastructure