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
Figure 8.4: Average Repository Water Saturation for All WL Cases
These results indicate that, for the majority of the cases considered, the repository will be largely unsaturated for a very
long time due to:
� the slow supply of water from the rock due to its very low permeability (and low porosity);
� the slow supply of water from the sealed shafts due to their low permeability and low total area;
� consumption of water by various anaerobic reactions involved in degradation of organics and metals; and
� the pressure of the gas ‘bubble’ formed from the degradation of the wastes and retained by the low
permeability rock and sealed shaft.
In support of this conclusion, it is also noted that there is observational evidence from excavations elsewhere in Ontario
that the host rock formation is expected to be virtually dry. In particular, the cooling water intakes to the Darlington
nuclear station were excavated through the Cobourg Formation where it outcrops in eastern Ontario. After excavation,
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