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
OPG Response:
This response was prepared in consideration of the reference to Information Request (IR) EIS-02-34 (OPG 2012a). It
is assumed, based on that response, that zones of mineralization refers to the Ordovician shales that are intersected
within the vent and main shaft only and represent approximately 4% by volume the rock to be placed in the Waste Rock
Management Area (WRMA) and which will be stored in a temporary stockpile within the WRMA. GOLDER (2011,
Table 3) reports that the highest concentrations of trace metals (As, Cu, Co, Ni, Pb, Tl and Zn) are found in the shale
sequence.
As reported in GOLDER (2011) and in OPG’s response to IR-EIS-03-96 (OPG 2012b), the results of short-term
laboratory leach testing indicate a potential for some metals (aluminum, boron, cobalt, thallium and vanadium) to leach
at concentrations slightly above the Provincial Water Quality Objectives (MOEE 1994). However, these tests are
considered to be conservative and not fully representative of weathering and other processes likely to occur in the field.
Further preliminary water quality modelling being completed in support of the design of the stormwater management
pond has identified no potential concerns with metals in the stormwater pond discharge as a result of leaching from the
waste rock.
Kinetic testing is designed to provide an indication of how materials will react over time. For sulphidic materials,
humidity cell testing is the standard kinetic test that measures the weathering of sulphide minerals. Other kinetic tests
are intended primarily to measure secondary mineral precipitation and dissolution weathering characteristics (MEND
2009). Neither of these tests are directly applicable to the DGR Project because much of this testing is directed
towards characterizing sulphidic materials in areas of mineralization, which as described above, are not observed in
large quantities at the DGR site and are therefore not expected to control the drainage chemistry. In addition, these
kinetic lab tests have inherent uncertainties and, when the results are applied to predictive modelling, would not provide
more certainty than the short-term leach results. In fact, the short-term leach results have been used in a conservative
way because it was assumed that the concentrations leaching from the waste rock are the same through the life of the
project, and do not decrease with time as would be expected.
The guidelines presented in Price (1997), MEND (2009) and INAP (2012) are largely meant for geochemical
characterization of sulphidic deposits and advocate for a phased approach with respect to geochemical
characterization. Static testing (which includes short-term leach testing) is the first phase of geochemical
characterization, and is a precursor to kinetic testing. Kinetic testing is commonly required to assess the relative rates
of the various acid rock drainage and metal leaching reactions over time. Field-scale leach tests may be initiated to
provide a better representation of material reactivity for specific waste rock management area conditions. Kinetic
testing is typically only performed if static tests indicate a potential for acid generation or metal leaching. Given that the
results of the geochemical testing (GOLDER 2011) indicated no potential for acid generation, the overall sulphide
content was low, and the leachate concentrations were not significantly above the criteria (Provincial Water Quality
Objectives), kinetic testing was not recommended.
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