Pierre River Mine Project

WATER AENV SIRS 15 – 43
Section 12.1
Request 25b Explain why flood attenuation is the only hydrological characteristic discussed
when flooding is only one of a suite of hydrological events affiliated with
wetlands.
Response 25b Typically, hydrologic characteristics of wetlands (muskeg, peatlands or forested
swamps) include considerable storage of precipitation runoff, considerable
evapotranspiration and low runoff yield. In addition, these features attenuate
large floods that extend to the flood plains.
In general, the removal of wetland features within the mine footprint will result
in reduced flows (i.e., water yield), including flood flows to receiving streams
and rivers. However, the hydrologic effect of removal of wetlands will be on
reduced flood attenuation capacity.
Request 25c The sustainability of a wetland’s structure and function is highly dependant on
sustaining the hydrodynamics of the wetland. Further clarify how wetland
integrity will be maintained in relation to other key hydrodynamic
characteristics, such as seasonal fluxes in mean low and mean high water levels,
and in relation to typical interactions with wetland vegetation, for example,
altered vigor or desiccation effects.
Response 25c Wetland hydrodynamics in the Pierre River Mine local study area (LSA) may be
affected by a variety of site-specific factors. However, by assessing the effects of
the drawdown on wetlands using a 0.1 m drawdown contour, the environmental
consequences of drawdown on wetland function are estimated conservatively. In
addition, a wetlands monitoring program will be implemented to determine the
specific effects the drawdown has on Pierre River Mine wetlands. The EIA,
Appendix 5-6, Terrestrial Monitoring Programs, Section 4, page 8, describes the
general wetlands monitoring program that will be implemented to determine
potential change to wetlands associated with the project. If monitoring indicates
that additional mitigation is necessary, the monitoring results will be used to
develop site-specific adaptive management strategies.
Request 25d Four items are listed that qualitatively describe drawdown effects on the
hydrology of the remaining wetlands. In relation to wetland functionality
provide additional supporting evidence (e.g., data, logical arguments, relevant
literature citations).
i. Compare observations of the hydro-dynamic character of adjacent
undisturbed wetlands in relation to remaining affected wetlands;
ii. Use observations from adjacent undisturbed wetlands regarding normal
wetland succession, to better characterize the time it will take for remaining
affected wetlands to “…return to their former functionality more quickly”;
12-32 Shell Canada Limited April 2010
CR029