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
parameters. These targets, while not meant to be effluent criteria, have been used to guide the design the SWMP and
develop mitigation measures to avoid significant environmental effects.
Following submission of the EIS (OPG 2011b), water quality modelling has been performed as part of the design of the
SWMP and this modelling has identified salinity (as measured by TDS) and nitrogen compounds as the two water
quality issues that may require additional mitigation. Particular attention will be paid to salinity and nitrogen compounds
when developing water quality criteria.
7. Water Treatment
Water quality modelling done as part of the design of the SWMP has identified potential water quality issues related to
salinity from the groundwater entering the shafts, and nitrogen compounds from blasting residues. Release of nitrogen
compounds would cease once all blast residue is flushed from the waste rock pile, likely within a few years after the last
waste rock is placed on the pile.
Several options, largely related to source reduction or elimination, will be explored to ensure the concentrations of
salinity and nitrogen compounds are below acceptable levels in the SWMP discharge. To manage salinity, the Salina
A1 and Guelph formations can be grouted to reduce or eliminate groundwater inflow from these formations. To
manage nitrogen compounds in SWMP discharge, use of emulsion will be maximized and best-blasting practices will
be implemented to minimize amount of blast residue left on the waste rock. In the remote event that source reduction
or elimination cannot reduce concentrations to below acceptable levels in the SWMP discharge, then a final mitigative
option of treatment would be implemented. The need for treatment would be identified through the results of a
monitoring program. The results of the monitoring will be coupled to criteria, established through relevant regulatory
processes described above, which will ensure there are no significant adverse effects to the environment.
Should treatment be required to remove salinity, the saline groundwater would be collected and treated prior to entering
the SWMP. Saline groundwater could be collected at the bottom of the shafts and then be taken to ground surface
where it would be treated, by example, with an evaporator. Water could be released from the evaporator as either
steam or distilled water. If water, it would then be directed to the SWMP. Any run-off water from the waste rock pile
that has elevated nitrogen compound concentrations could be treated by, for example, aeration in the SWMP. If
implemented, treatment for aforementioned dissolved constituents would ensure effluent from the SWMP meets the
discharge criteria.
8. Stormwater Management Pond – Operation
The stormwater management system has been designed to retain runoff during storm events, and control the
suspended solids concentrations in effluent discharges. In between storm events, the stormwater management system
will be used to control suspended solids concentrations primarily from underground sources. Treatment for suspended
solids concentrations will be achieved by the provision of retention and a permanent pool in the SWMP (see Item #5
above for further details).
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