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
EIS-04-101 � Section 8.1,
General
Information and
Design Description
� Section 8.2, Site
Preparation and
Construction
� Section 8.3,
Operation
� Section 10.1.1,
Geology and
Geomorphology
� Section 10.1.2,
Surface Water
� Section 10.1.3,
Groundwater
OPG Responses to the Final Sub-set of IRs from Joint Review Panel IR Package #4
Information Request and Response
Information Request:
Provide the calculations, assumptions and confidence limits behind the estimates of maximum excavation water
discharge and sump water pumping.
Context:
No context required
OPG Response:
The maximum excavation water and sump water pumping discharge estimates considered in the Environmental Impact
Statement (EIS) (OPG 2011, Section 4.7.5.4) was 5.4 L/s. Further assessment of groundwater inflows during
construction has been completed incorporating new information collected from recent site investigation programs for
groundwater inflows in the top 200 m during shaft sinking (see response to Information Request (IR) EIS-01-01 in OPG
2012a), and following full installation of shaft liners (see response to Undertaking TIS-11 in OPG 2012b). Calculations,
assumptions and confidence limits are detailed in the referenced reports below. The other major contributor to the
underground water discharge is the use of process water for equipment, construction and dust mitigation which has
been reassessed. The amount of condensate that could report to main sump has also been reassessed.
The groundwater inflow modeling that was recently completed (Sykes 2012) incorporates a grout curtain (or annulus)
around the shafts. The grout curtain is assumed to be 3 m thick with a hydraulic conductivity of 10 -7 m/s. The
estimated groundwater inflows while sinking through the top 200 m are in the range of 2 to 4 L/s (OPG 2012a). A
sensitivity analysis was conducted for a grout curtain performance of 10 -6 m/s. In this case, estimated groundwater
inflows were much higher. However, it would not be possible to sink the shaft with such high water inflows and
therefore additional ground treatment would be applied, either from surface or by in-shaft cover grouting, until the target
maximum inflow of 3 L/s was met (refer to response to IR-LPSC-01-31 in OPG 2012a for additional information about
proposed ground treatment).
The groundwater inflow modeling for fully-lined shafts (GOLDER 2012) shows a significant reduction in expected
groundwater inflows. The expected inflow of 0.45 L/s is approximately a factor of 3 lower than the groundwater inflow
estimate assumed in the development of the EIS. This inflow could be further reduced through in-shaft grouting of the
Salina A and Guelph Formation horizons.
The usage of process water for equipment, construction and dust mitigation during construction has been re-estimated
and is now assumed to be about 20 L/s (average). This estimate is very conservative to allow for a wide variety of
equipment selection and water demand criteria. The estimate has been derived using high water demand equipment
(e.g., high efficiency multi-boom drilling jumbos), high utilization estimates for operating hours per day, continuous
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