Potassium Effluent Quality Criteria Water Licence Amendment - - PowerPoint PPT Presentation

Potassium Effluent Quality Criteria Water Licence Amendment Application Public Hearing, February 8, 2018

Dominion Diamond Ekati ULC

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Presentation Overview

• Water Licence Amendment Request
• Environmental Protection at the

Ekati Diamond mine

• Intervention Recommendations and

Responses

• Summary

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Water Licence Amendment Application

• Dominion is requesting that potassium EQC at the Ekati Diamond Mine be aligned

with the approved Site Specific Water Quality Objectives (SSWQO)

• Maximum Average EQC = 64 mg/L
• Maximum Grab EQC = 103 mg/L
• SSWQO represents our best understanding of environmental risk associated with

potassium toxicity

• Reflects current state of science including recently published and site-specific data
• Consistent with the WLWB’s Water and Effluent Quality Management Policy
• Direct link between receiving environment guidelines/objectives and EQC
• Facilitates clear and consistent interpretation and application of Licence requirements
• Consistent with process for establishing EQC at the Ekati Diamond Mine
• Provides consistency between Water Licence and the Potassium Response Plan
• Current EQC is not reasonably achievable

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Environmental Protection at the Ekati Diamond Mine

• Dominion has rapidly identified and responded to concerns over potassium at the

Ekati Diamond Mine and is committed to ongoing adaptive management

• Adaptive management of environmental change at the Ekati Diamond Mine is

governed by many layers of environmental protection aimed at ensuring Significance Thresholds are not reached

• A level of environmental change in any monitored variable which, if reached, would result in a

significant adverse effect Effluent Quality Criteria AEMP Benchmark

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Minewater Management Facilities (e.g., LLCF) Receiving Environment (e.g., Leslie Lake) Site-specific Water Quality Objective (SSWQO)

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Water Quality

Environmental Protection at the Ekati Diamond Mine

Phytoplankton Zooplankton Fish Wildlife and Humans Sediment Quality Benthos

Aquatic Effects Monitoring Program

• A comprehensive, early-warning

monitoring program designed to detect change in aquatic ecosystems Aquatic Response Framework

• An early-warning system with defined

action levels that are initiated within an adequate timeframe to prevent the

• ccurrence of significant adverse

environmental impacts

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Mine Operations

Significance Thresholds Levels of environmental change which, if reached, would results in significant adverse effects AEMP Benchmark = SSWQO = 64 mg/L If exceeded could result in localized sublethal effects

Potassium Concentration

Medium High Low

Action Levels

Environmental Protection at the Ekati Diamond Mine

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Recommendations and Responses

• ECCC Recommendation 1,2 and

IEMA Recommendation 1

• Rationale on how exceedance of

the SSWQO in the aquatic receiving environment are protective of the aquatic environment should be provided.

• If higher concentrations in the

receiving environment are demonstrated to be protective, an updated potassium SSWQO should be provided.

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Recommendations and Responses

• Dominion Response
• EQC established using ‘Use-Protection Approach’ consistent with

WLWB Water and Effluent Management Policy

• Best protection of the receiving environment is through the integration
• f several site-specific protection measures
• EQC, AEMP, ARF
• Action levels defined in the ARF allow management actions to be

initiated within an adequate timeframe to prevent reaching a significance threshold

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Recommendations and Responses

• Dominion Response
• Exceedance of SSWQO does not necessarily imply that aquatic

biota will be adversely affected

• SSWQO is conservative, and scientifically defensible (developed with the most

recent best available data using CCME guidance)

• A potassium concentration at which a sublethal effect would be expected to the

most sensitive species would exceed 100 mg/L

• Modelling results indicate potential minor short-duration, under-ice exceedances

in Leslie and Moose Lakes—small natural catchment area

• No update to the SSWQO is required at this time
• The aquatic receiving environment has been shown to be resilient to

changes in water quality

• e.g., Aquatic Effect Synthesis results

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Recommendations and Responses

• GNWT Recommendation 1,2,3
• The GNWT recommends that a 42‐day toxicity test be undertaken using

Hyalella azteca to evaluate survival, growth, and reproductive endpoints using site water spiked with potassium concentrations at minimum 64 mg/L, 80 mg/L and 100 mg/L to evaluate the response of this sensitive species.

• The GNWT recommends that a 30‐day early life stage test be conducted on

fathead minnows using site water spiked with potassium concentrations at minimum 64 mg/L, 80 mg/L and 100 mg/L to evaluate hatching success, survival, growth, biomass, and gross morphological alterations.

• The GNWT recommends that toxicity testing be conducted on a freshwater

bivalve using site water spiked with potassium concentrations at minimum 64 mg/L, 80 mg/L and 100 mg/L.

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Recommendations and Responses

• Dominion Response
• The toxicity tests completed for the development of the long-

term SSWQO are considered long-term duration tests (CCME 2007)

• The additional toxicological tests proposed by GNWT-ENR present

technical and administrative challenges

• Additional reproductive end-point not warranted
• Fingernail clams are not commonly used species in laboratory test—no

standardized test methods

• Minimum of six months to complete additional testing
• Additional toxicity tests would cause unnecessary delay

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Recommendations and Responses

• GNWT Recommendation 4
• Given that potassium concentrations are not trending towards the

higher EQC at the KPSF and Desperation Pond and there are uncertainties associated with the application of the Koala watershed SSQWO for potassium in these areas, GNWT recommends that the potassium EQC of 64 mg/L not be applied for these areas. Should there be an apparent operational need in the future, and technical uncertainties be resolved, the GNWT would support this matter being reconsidered by the Board.

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Recommendations and Responses

• Dominion Response
• Site-wide recommendation for the EQC consistent with WLWB decision
• n the revision of the SSWQO to 64 mg/L
• Reflects the current state of science for potassium toxicity
• The SSWQO was derived solely on potassium toxicity data following

CCME methods

• No exposure and toxicity modifying factors have been definitively

defined for potassium

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Recommendations and Responses

• IEMA Recommendation 2
• Dominion Diamond should

clarify whether water treatment is a feasible alternative to reduce potassium concentrations in water discharged at SNP stations 1616-30, 1616-43 and 1616-47

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Recommendations and Responses

• Dominion Response
• Water treatment options (reverse-osmosis and ion exchange) have

high costs and their own environmental concerns

• Problematic by-product (brine) management
• High fuel consumption and associated greenhouse gas emissions
• Significant additional capital and operating costs
• Discharge that is environmentally protective can occur without

treatment

• Amending the EQC to 64 mg/L would provide greater operational

flexibility to manage water, while the AEMP and ARF will ensure actions continue to be taken to maintain environmental protection

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Summary

• Short- and long-term SSWQO are protective of the receiving environment at the

Ekati Diamond Mine

• Updated and revised SSWQO have been extensively reviewed
• Long-term SSWQO is already in use at the Ekati Diamond Mine
• Current potassium EQC of 41 mg/L is not reasonably achievable
• Alignment between EQC and SSWQO of 64 mg/L is:
• appropriate and protective of the receiving environment; and
• consistent with WLWB policy and with the established process of setting EQC at

the Ekati Diamond Mine

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Dominion Diamond Ekati ULC

Thank You