Report - Agence canadienne d'évaluation environnementale

Assessing the risks related to the project
Since an LNG tanker would navigate at some 500 m from île d’Orléans, the closest
distance to the shore on its route before arriving at the terminal, a natural gas cloud
could theoretically reach certain inhabited areas of the island if the LNG pool would
not immediately ignite after a spill. Also, the Panel notes that, with an LNG tanker
approaching the planned jetty, a vapour cloud could also reach the shoreline
population in certain places in the sector of Lévis-Beaumont, when using breaches of
750 mm and 1,500 mm, assuming a steady-state spill pool and without immediate
ignition. In this respect, the proponent stated that such a cloud would spread at
relatively low altitude. Should this cloud reach an ignition source, it would ignite and
the fire would travel back in the direction of the LNG tanker. Under these
circumstances the thermal impact would only be serious for someone within the cloud
(Mr. Glenn Kelly, DT3, p. 70 and 75).
Environment Canada also reported that it couldn’t perform the modelling of an
accident generating a natural gas cloud which would spread towards the shores of île
d’Orléans. However, the Department was of the opinion that the risk was low and that
there are chances the cloud would disperse before reaching the shore and would not
ignite, depending on wind direction, its force and the possible presence of an ignition
source. In the event of a terrorist act or a collision, there would be an ignition source
with the resulting quick ignition of gas vapours and therefore, a gas cloud would not
spread (Mr. Robert Reiss, DQ75.1)
The CERL was also of the opinion that it was very unlikely a natural gas cloud would
separate from its source and travel over a distance that would be greater than the one
calculated by the proponent (DQ78.1).
♦ Finding — The Panel found that sensitive community elements could be exposed to
thermal radiation which could reach 5 kW/m 2 in the sectors of the east point of île
d’Orléans, of Saint-Laurent-de-L’Île-d’Orléans and of Lévis-Beaumont, when
considering collision or grounding scenarios, and using a steady-state spill pool and a
1,500 mm breach in an LNG tanker tank as modelling criteria.
♦ Finding — The Panel found that in the event of a collision or a grounding of an LNG
tanker, a liquefied natural gas vapour cloud could reach certain locations with
shoreline populations for île d’Orléans and for Lévis-Beaumont. However, the
probability of such an occurrence is low.
140 Rabaska Project – Implementation of an LNG Terminal and Related Infrastructure