hydrogeology, high lake rob dickin hydrogeologist, gll
TRANSCRIPT
Hydrogeology, High Lake
Rob DickinHydrogeologist, GLL
Overview
• Brief background
• Discussion of key issues
• Summary of commitments
• Recent comments– INAC– NRCAN– KIA
Background
• Bedrock Geology
• Lake Taliks
• Baseline Data Collection
• Conceptual Model
• Groundwater Model
•Felsic to ultramafic metavolcanics (country rock)
•Intrusive hornblend/biotite granodiorite
•Diabase dykes
Hydrogeological Conceptual Model: Vertical north-south trending bedding planes
Bedrock Geology
2005 Drilling in West Zone
Winter Drilling into High Lake Talik
Hydrogeological Field Program
• Packer tests in five boreholes
Country Rock, High Lake Talik
Hydrogeo Conceptual Model
Structure of the Groundwater Model
Gw flow
Groundwater flow beneath permafrost
Lakes with through talikShaded dark blue
Overview of Recent Comments
Recommendations and information requests raised on Nov. 23, 2007 by
• INAC review
• NRCan (reviewers 1, 2, 5)
• KIA (Rescan review team)
• Note: past comments responded to from Environment Canada
Key Issues Identified
• Issue 1. Shallow seepage from High Lake TCF to lakes L15 and L4 (Granite L.)
• Issue 2. Groundwater transport and attenuation from High Lake TCF to Kennarctic River and Granite Lake (L4)
• Issue 3. Potential for groundwater seepage into West Zone underground mine ramp near or beneath lakes L12/L14/L22
Issue 1. Shallow Groundwater Seepage
• Issue #1 Potential for shallow groundwater seepage in active layer from High Lake TCF to lakes L15 and L4 (Granite L.)
• This issue involves permafrost engineering and water quality in TCF as well as hydrogeology
• Following 4 slides will help with discussion
Shallow Groundwater Flow from High Lake
Attachment to INAC_58 response
Permafrost Aggradation
Attachment to NRCAN_6 response
L15 L4
Assumed Depth of saturated flow, Ds (m)
5 5
Width of flow, W (m) 183 38
Ave. Distance between High Lake and receiving environment dx, (m),
183 130
Hydraulic conductivity, (m/s) 10-5 10-5
Seepage Parameters
To L15 To L4
year 1 5.6 8.4
year 2 1.3 1.1
year 3 2.0 1.3
year 4 to year 30 2.2 1.3year 31+
22 13
Estimated seepage from High Lake by year, m3/day
Issue 2• Attenuation of contaminants along
deep groundwater pathway from High Lake TCF to Kennarctic River and Granite Lake (L4)
• Involves water quality in High Lake TCF
• Clarify and discuss
• Following 4 slides for assisting discussion
Groundwater flow from High Lake Talik
Observed concentration reduction takes place over the first segment of the groundwater flow pathway (about 25 m).
Additional attenuation capacity is available in the remaining section of the flow path from Kennarctic River to High Lake (about 800 m).
Salinity and trace metal transport• Geochemical batch modeling in
PHREEQC-V2
• Cadmium – affected by salinity due to complex formation
• Zinc and copper – no change due to complex formation
Geochemical Modelling
• Simplified assumption that attenuation is primarily due to surface complexation onto hydrous ferric oxides (HFO’s)
• Two scenarios were simulated for cadmium complexation– (1) baseline - existing cadmium attenuation
was matched by adjusting the concentration of surface sites
– (2) future: attenuation capacity of cadmium in the presence of higher salinity was assessed using the calibrated parameters
Effect of salinity on attenuation
•Cadmium attenuation decreases in presence of salinity from a factor of 33 4•Result of a chloride-cadmium complex that does not readily attenuate
Issue 3
• Potential for groundwater seepage into West Zone underground mine ramp near or beneath lakes L12/L14/L22
• Involves mine planning, grouting, hydraulic conductivity testing
• 12 m of permafrost and 70m of rock• following slide shows section for
discussion
L12/L14/L22 groundwater seepage
List of Hydrogeology Commitments by Proponent
1. Collect additional hydrogeology baseline data 2. Update and recalibrate MODFLOW model 3. Improve assessment of mine inflow quality after
obtaining samples from beneath permafrost in year 5
4. Improve assessment of shallow groundwater flow from High Lake TCF to L15/L4 after collecting shallow groundwater baseline data (Key Issue #1)
5. Implement long-term permafrost monitoring program
6. Reassess transport of contaminants from TCF to receiving environment after collection of additional baseline water quality data
New Baseline Data
• new data for MODFLOW model update includes:
• ground temperature (permafrost)data, • groundwater lake leakage rates, • hydraulic conductivity data, • hydraulic head data• update model with new data by the end
of year 5
INAC Hydrogeology Overview
• INAC made 5 recommendations to improve the hydrogeological assessment
• Of the original 12 information requests, 10 responses were accepted
• Issue for discussion identified within shallow groundwater assessment (key issue #1)
INAC Rec #33: Hydrogeology Model
• Recalibrate flow and quality groundwater model with additional baseline data:– Three talik groundwater samples and K values– K values and pressure from four West Zone
boreholes drilled by year five– Sample deep groundwater quality– K values in shallow active zone around the
perimeter of High Lake
• Zinfex accepts recommendation #33
INAC Rec # 34: Climate Change
• INAC recommends that a monitoring plan be put in place to monitor the permafrost condition on a long-term basis.
• The additional information gathered should be included in the periodic updates to the groundwater model.
• Zinfex accepts recommendation #34
INAC Rec #35: Groundwater Contamination• Assessment of groundwater impacts
resulting from facilities / activities such as the use of chemicals, and the potential for contaminant releases into the environment, such as from spills
• Provide a monitoring and mitigation plan for groundwater protection related to these facilities / activities
• Clarify and discuss recommendation
INAC Rec #36: Environmental Impacts
• Assess additional contaminants of concern that may be present in High Lake during operation and closure
• Identify whether there are other issues / contaminants that may be of concern
• Impact predictions and associated mitigation measures should be revisited as further site specific information becomes available
• Monitoring and mitigation plan for closure should be updated
• Clarify and discuss recommendation
INAC Rec #37: Monitoring
• The final EIS should include further detail on the groundwater monitoring program, and
• Indicate the mechanism whereby the monitoring results will be used to update and verify/ calibrate the groundwater model.
• Clarify and discuss recommendation
Remaining INAC IR Issues
• INAC #50: Plans were outlined to obtain additional baseline hydrogeology data (agreement has been reached)
• INAC #57: Proponent should outline mitigation measures that can be applied if the operational measures are not sufficient to maintain permafrost beneath L12/L14/L22 (key issue #3)
NRCan Review Nov 23
• Reviewer 1, issues A3 and A4
• Reviewer 2, Issues B1, B3, B4
• Reviewer 5, issue E2
NRCan Reviewer 1
• A3: protecting L15 and L4 from shallow seepage from TCF – thermal issues need to be resolved before the
groundwater issues can be addressed (discussion with Jim Cassie for Key issue #1)
• A4: protecting L12/L14/L22 from closed talik becoming and open talik – comments are helpful for resolving issue
(discussion with P. Davis for key issue #3)
NRCAN Reviewer 2
• B1 is similar to A4, key issue #3• B3 follows A3, key Issue #1
– Leslie Gomm required for discussion of longer term closure and monitoring requirements
• B4 is key issue #2– Attenuation argument has uncertainties.
Zinifex could assess pathway with no attenuation,
– Zinifex has committed to reducing uncertainty by sampling additional talik water under HL
– Tailings cover issues (LG)
NRCAN Reviewer 3
• E2 is similar to B4 (Key Issue #2)– Zinifex has agreed to sample more
groundwater (Conclusion No. 3)– Zinifex is not planning to define the
elemental transport and attenuation mechanism for this level of the permitting process
KIA Review
• 11 of the thirteen issues raised by the KIA are dealt with in Volumes 1 to 11 of the DEIS– Detailed response can be provided if required
• Issue 45: Arbitrary assumption of one order of magnitude variation in hydraulic conductivity– Proponent commits to complete the sensitivity analysis
recommended by KIA in future modelling.
• Issue 51: Attenuation modeling based on one sample– Rescan suggests a conservative assumption would be
to consider no attenuation…– Similar to NRCAN B4 issue (Key Issue #2). Further talik
groundwater sampling will be completed.
End