Dominion Diamond Ekati Application to Amend Potassium EQC Water - PowerPoint PPT Presentation

Dominion Diamond Ekati Application to Amend Potassium EQC Water Licence Intervention W2012L2-0001 February 8, 2018

Site-Specific Water Quality Objectives • Concentrations or statements describing conditions to protect the most sensitive use of water at a site. • Modified to account for local aquatic conditions and organisms. • The revised short-term SSWQO is appropriate for application in instances where a short-term disturbance of the environment occurs (e.g., a spill). The revised long-term SSWQO is appropriate for monitoring of receiving environment quality, and is expected to be protective of aquatic life for long-term exposures. (DD 2015)

Effluent Quality Criteria for Potassium Issue: EQCs for potassium should be established so that short-term and long-term SSWQOs are achieved in the receiving environment. Dominion Diamond Conclusion: EQCs for potassium should be amended to 64 mg/L (max. average) and 103 mg/L (max. grab) despite model predictions that short- term SSWQO will be exceeded in Leslie and Moose lakes.

EQC for Potassium Agency Conclusion: Increasing trend in potassium in process plant discharges. Water discharged from LLCF predicted to approach proposed maximum average EQC for potassium in 2029 before declining. Water under-ice in Leslie and Moose lakes predicted to exceed long-term SSWQO for potassium over the next four years and again starting in 2036 before declining.

EQC for Potassium

EQC for Potassium

EQC for Potassium Agency Recommendation: The WLWB establish Effluent Quality Criteria for potassium in condition H.20(a), (b) and (c) at levels that ensure short-term and long-term SSWQOs are not exceeded in the downstream environment at any time, including the annual under-ice period.

Alternative Source Reduction Options Issue: WLWB Effluent Quality Management Policy objectives: Waste Minimization and Pollution Prevention. Dominion Diamond Conclusion: Modelled increases in potassium concentrations and loadings from LLCF water cannot be avoided as no source control mitigation is possible.

Alternative Source Reduction Options Agency Conclusion: BHPB review of aquatic protective measures (2012) concluded: Reverse osmosis typically provides a 95-99% reduction in all forms of anion and cation concentrations Unclear whether effluent treatment for potassium has been assessed as part of current application.

Alternative Source Reduction Options Agency Recommendation 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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