Ontario Power Generation's Response to the Joint Review

Attachment 1 to OPG letter, Albert Sweetnam to Dr. Stella Swanson, “Deep Geologic Repository Project for Low and Intermediate Level Waste – Submission of
Responses to the Final Sub-set of Package #4 Information Requests”, CD#: 00216-CORR-00531-00143.
IR# EIS Guidelines
Section
Information Request and Response
include examination for hydrocarbon occurrence that may require mitigation within the waste rock management area
(WRMA).
As described in the response to Information Request (IR) EIS-04-159, the guidelines presented in MEND (2009) are
largely meant for geochemical characterization of sulphidic deposits and are not entirely applicable to the DGR Project.
However, waste rock testing will include elemental composition (by aqua regia digestion and XRF), acid-base
accounting, and short-term leach testing (modified from ASTM D3987 for a 4:1 water to rock ratio).
Waste rock monitoring will be concurrent with surface water quality monitoring and each will complement and inform
the other. Surface water samples will be submitted for laboratory analysis for metals, anions and salinity, among
others, and will provide additional assurance that the waste rock and its leachate have been accurately characterized.
These data will also provide information that can be used to design additional mitigation measures if required.
At least one surface water monitoring location will be sited immediately downstream of the WRMA in order to
characterize the runoff prior to discharge to the stormwater management pond. Samples will be collected quarterly at a
minimum throughout the site preparation and construction phase as described in the EA Follow-up Monitoring Program.
Depending on the results of the rock monitoring program described above, additional surface water samples may be
collected in order to further characterize “first flush” events (spring runoff and the first rainfall after a prolonged dry
period). Because of the variability of site conditions (waste rock characteristics and seasonal variations in precipitation
and runoff events), the timing and frequency of the sampling will be determined in the field to best observe and
understand the characteristics of the WRMA runoff.
If the waste rock monitoring program results indicate that the rock leachate varies significantly from predicted
characteristics, continuous monitoring at the surface water monitoring location may be implemented. A water quality
monitor may be used in the field to measure electrical conductivity (EC) and pH. The EC values can be plotted against
rainfall events; changes in EC could be correlated to the laboratory analysis and could potentially be used to identify
trends in water quality.
The groundwater monitoring program described in the EA Follow-up Monitoring program includes routine (quarterly)
sampling from monitoring wells situated in the uppermost aquifer immediately downgradient of the WRMA. This
groundwater monitoring, implemented in 2012 to establish baseline and background conditions, would allow the
influence of WRMA operation on groundwater quality to be observed, were it to occur.
As shown on the surface facility layout in OPG’s presentation to the Technical Information Session on July 18, 2012
(OPG 2012, Slide 11), the waste rock will be segregated at surface into three areas based on the type of rock
(dolostones, shales, limestone). The shale and dolostones resulting from the shaft excavations will either be reused
onsite or covered within one year of excavation, therefore further segregation is not proposed. Additionally, the rock
reused in berms will be covered, providing further means to manage and redirect runoff.
The majority of the waste rock will come from the excavation at the repository level. During the first year of
underground development, the volume of rock excavated will be relatively small. Monitoring results characterizing the
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