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