Report - Agence canadienne d'évaluation environnementale

Impacts on the natural environment
♦ Recommendation 20 — The Panel recommends that, subject to an agreement with
Fisheries and Oceans Canada and the ministère des Ressources naturelles et de la
Faune, the proponent determine the water supply sources for the hydrostatic tests on
the pipeline pipes and this, at the environmental assessment phase. This choice
should comply with the minimum ecological instream flow regimes of the bodies of
water concerned. If needed, mitigation or compensation measures should be taken to
reduce impacts on fish habitat.
Potable water wells
The analysis of the project’s impacts on groundwater was conducted by delineating
two areas likely to be affected, namely LNG tanks (area A), where an excavation
exceeding 10 m would be planned, and the access road to the jetty (area B), which
should be excavated in rock north of Highway 132. These areas are shown on
Figure 13. Aside from the potential impact on surface water, the groundwater body
drawdown could affect potable water well levels belonging to residents in the area.
According to the proponent, the aquifer of the basement rock supplying the residents has
only limited natural protection. Only the residents living west of the junction between
Lallemand Road and Highway 132 and those living on rue Jean-de-Brébeuf are served
by the aqueduct and the sewer, while the others rely on individual installations. The
proponent has defined a perimeter of influence where the wells would be likely to undergo
a drawdown exceeding 0.5 m. The perimeter covers approximately 4.5 km 2 .
The groundwater drawdown in area A would be caused by excavation of the access
road to the jetty, including the dynamiting of part of the cliff. According to the
proponent’s analyses, the water level in the wells of some twenty residences could be
influenced by the drainage of the access road to the jetty.
In area B, the groundwater body drawdown would be caused by excavation for the
tanks and pumping to keep their bases dry during the operation phase. In the tank
basin drainage influence perimeter, well levels of some fifteen residences could
experience a drawdown less than 1 m. The same would apply to the Transit
campground located south of Expressway 20 (DA22.1, p. 13).
The proponent has conducted a preliminary characterization of some of the residents’
wells. A more comprehensive inventory as well as a complete portrait of the
groundwater physicochemical and bacteriological quality would be established once
the project is authorized. The proponent committed to following-up on groundwater in
order to ensure that the project does not jeopardize either the availability or the quality
of groundwater for present and future users.
Rabaska Project – Implementation of an LNG Terminal and Related Infrastructure 209