Miramar Northern Mining Limited - Con Mine Remediation MV2017L8-0008 - PowerPoint PPT Presentation

Miramar Northern Mining Limited - Con Mine Remediation MV2017L8-0008 Technical Workshop July 4 and 5, 2018 1

How Did We Get Here? • Water Licence Submission Dec 2017 • First Technical Session March • EQC, modelling, monitoring 1/2 • Discharge Criteria Concept Meeting • Discussion on how to address stakeholder concerns, focus on March chloride 23 • Technical Workshop • Overview of approach May 23 • No results at that time • Second Technical Session • New limits for chloride • Proposed delineation of regulatory mixing zone June 15 • Additional monitoring – plume study and AEMP Peg Lake 2017 2

Additional Studies Since March 2018 Effluent Quality Criteria for Chloride 1. Lab Study - Site-specific acute toxicity threshold for chloride using site-relevant waters 2. Desktop Study - Chronic SSWQO for chloride in the downstream receiving waters 3. Model chloride concentrations in receiving water for different loading scenarios 4. Develop EQC for chloride Regulatory Mixing Zone 5. Propose mixing zone boundary Future Monitoring 6. Develop Draft AEMP 3 Meg Lake 2017

Where to Find the Material - EQC Task Main Appendix Appendix Appendix Report 1 A B C  Effluent Quality Criteria for Chloride  Develop a site relevant acute threshold for chloride  Evaluate proposed chronic SSWQO for chloride  Model chloride loading scenarios in M-K-P lakes & Jackfish Bay  Compare predictions to site-specific acute threshold & SSWQO  Regulatory Mixing Zone within Jackfish Bay  Compare model predictions to SSWQO  Evaluate sampling depths and accessibility  Future plume validation and monitoring 4

Where to Find the Material - AEMP Section in Main Report 2 Description 1.0 Introduction Background and regulatory framework 2.0 Site Characterization Characterization of site, treated effluent discharge and receiving water 3.0 Conceptual Site Model Identification of stressors, environmental pathways, receptors, measurement and assessment endpoint 4.0 Study Design Outline of study area, components, and sampling locations, frequency, and type 5.0 Response Framework Development of significance thresholds, Action Levels and potential response if Action Levels triggered 6.0 Reporting Requirements for AEMP reporting 2 Report on Draft Aquatic Effect Monitoring Program Outline (Golder 2018b) 5

Additional Chloride Toxicity Studies Completed Keg Lake 2017 6

Acute Chloride Toxicity Study - Overview Objective : Identify acute toxicity threshold of chloride , in a site-relevant mixture  Effluent and downstream receiving environment samples frequently exceed short-term CCME WQG (640 mg/L Cl)  Future chloride concentrations in treated effluent are uncertain, but could be higher than recent concentrations  A site-specific threshold for acute chloride toxicity will help inform water management decisions and non-lethality is met at compliance and monitoring stations 7

Acute Chloride Toxicity Study – Study Design 1 Collected representative base water from Peg Lake Measured base chemistry — Treatments were amended in-lab to achieve total 2 chloride targets (base plus amendment) using mixture-specific recipes Conducted spiked chloride tests: 3 D. magna (48-h), O. mykiss (96-h) Mixture A Mixture B Mixture C Exposure Scenarios Low SO 4 Moderate SO 4 High SO 4 Target chloride levels (mg/L): Lab Control Lab Control Lab Control Standard laboratory negative control (high hardness) Site chloride A 0 B 0 C 0 Base water (unamended) Cl - approximately 1,500 A 1 B 1 C 1 Base water plus low chloride equal across 2,500 A 2 B 2 C 2 Base water plus moderate chloride treatment levels, but relative ionic 3,500 A 3 B 3 C 3 Base water plus high chloride composition differs among Mixtures A, B 5,000 A 4 B 4 C 4 Base water plus very high chloride and C 8 8

Acute Chloride Toxicity Study – Study Design Mixture B  Reviewed current and future, modelled ionic composition  Study focused on chloride and sulphate  main constituents of interest  exhibited largest variance  Selected 3 ion composition mixtures Mixture C 9

Acute Chloride Toxicity Study – Study Design Mixture A 10 10

Acute Chloride Toxicity Study – Scenario Selections Ionic Composition (%) Scenario Mixture A Mixture B Mixture C Description Low Sulphate Moderate Sulphate High Sulphate Station SNP 0040-5 SNP 0040-1 SNP 0040-1 Time Period Existing Conditions Future Conditions Existing Conditions Average August to October Scenario 2 Maximum June to September (2015 to 2017) (2018 to 2028) (2015 to 2017) • • Description 10% SO 4 (of TDS) 33% SO 4 (of TDS) • 20% SO 4 (of TDS) • • 55% Cl 35% Cl • 49% Cl • • Represents dry conditions Current ion composition of • Intermediate mixture effluent 11 11

Acute Chloride Toxicity Study – Results D. magna Responses:  Test validity criteria met for all controls Survival (%)  Acute lethality occurred at chloride concentrations > Mixture A 2,500 mg/L in all Mixtures Mixture B  48-hr LC 50 (survival & Mixture C immobility) ranged from 2,894 to 3,086 mg/L Measured chloride (mg/L) Measured chloride (mg/L) 12 12

Acute Chloride Toxicity Study – Results Rainbow Trout Responses:  Variable response Survival (%) Survival (%)  Low, but acceptable control Mixture A mortality (10% mortality) Mixture B  No clear concentration- Mixture C response  96-hr LC 50 ranged from >4,820 to 5,220 mg/L Cl Measured chloride (mg/L) Measured chloride (mg/L) 13 13

Acute Chloride Toxicity Study – Discussion  Acute toxicity threshold should focus on D. magna as the more sensitive species For D. magna:  Threshold response in this study similar to published toxicity results (2,565 to 3,630 mg/L chloride; Elphick et al. 2011; Mount et al. 1997; Biesinger and Christensen 1972)  Toxicity results were generally similar across the mixtures  Acute chloride toxicity unlikely to occur under current, or future predicted conditions at concentrations ≤ 2,500 mg/L 14 14

Chronic Chloride Site Specific Water Quality Objective  Objective : validate interim chronic site-specific water quality objective (SSWQO) of 388 mg/L (derived using Elphick et al. 2011 hardness-dependent chloride equation)  Validation procedure: Reviewed recently published literature (2011 to 2018) for new toxicity data I. Multiple lines of evidence considered (e.g., approaches applied at northern mine II. sites) Applied site-specific conditions of environmental and toxicity modifying factors III. 15 15

Chronic Chloride Site Specific Water Quality Objective – Literature Review  New data from Streuwing et al. (2015) indicated high sensitivity of mayfly (Centroptilum triangulifer) to chloride under long-term exposure (14-d IC 25 dry weight = 138 mg/L)  Not a common test species but increasingly applied in freshwater toxicity testing (Conley et al. 2009; Xie et al. 2010) University of Iowa / www.discoverlife.org 16 16

Chronic Chloride Site Specific Water Quality Objective – Elphick et al. (2011) Model Elphick et al. (2011) Hardness-dependent Model  Conducted acute and chronic toxicity testing with nine freshwater species  Derived an HC 5 using species sensitivity distribution for tox data (15 species) collected under hardness of 80 to 100 mg/L (as CaCO 3 )  Additional toxicity testing indicated strong ameliorating effect of hardness on acute and chronic chloride toxicity  Derived a hardness-dependent equation, applicable over a water hardness range of 10 to 160 mg/L: Elphick et al. 2011 𝑋𝑅𝑃 = 116.63 𝑦 ln ℎ𝑏𝑠𝑒𝑜𝑓𝑡𝑡 − 204.9 Ceriodaphnia dubia response to chloride toxicity is positively correlated to water hardness 17 17

Chronic Chloride Site Specific Water Quality Objective – Con Mine SSWQO Elphick et al. (2011) model with Streuwing SSD with C. triangulifer data incorporated  Elphick equation remains an appropriate model (used for chronic SSWQO at Ekati)  Streuwing study of sufficient quality to include in SSWQO derivation and conducted under hardness range of 80 to 100 mg/L  Using Elphick approach incorporated IC 25 for C. triangulifer into chronic toxicity dataset  Derived an updated hardness-dependent equation, applicable over a water hardness range of 10 to 160 mg/L as CaCO 3 Updated hardness-dependent equation: 𝑋𝑅𝑃 = 79.02 𝑦 ln ℎ𝑏𝑠𝑒𝑜𝑓𝑡𝑡 − 138.28 18 18

Chronic Chloride Site Specific Water Quality Objective – Con Mine SSWQO Elphick et al. (2011) model with Streuwing SSD with C. triangulifer data incorporated  Median hardness at all locations in Jackfish Bay higher than calibrated range  SSWQO derived from maximum calibrated hardness (160 mg/L as CaCO 3 )  SSWQO = 260 mg/L Cl (rounded to two significant figures) Updated hardness-dependent equation: 𝑋𝑅𝑃 = 79.02 𝑦 ln ℎ𝑏𝑠𝑒𝑜𝑓𝑡𝑡 − 138.28 19 19

Additional Desktop Study Completed – Chloride EQC and Mixing Zone Keg Lake 2017 21

Chloride EQC and Regulatory Mixing Zone Outline of Chloride EQC and Regulatory Mixing Zone  Methods for determining chloride EQC and regulatory mixing zone  Incorporation of supporting chloride studies  Predicted concentrations in receiving water  Proposed EQC for chloride and regulatory mixing zone  Next steps 22 22