Mack Mackenzie V enzie Valle lley Land and W Land and Water Boar r Board Public Hearing Public Hearing Closure and R Closure and Reclamation Plan Par clamation Plan Part 2 2 and Monit and Monitoring ring Januar January 2020 y 2020
Water and r and Monit Monitoring at ring at Giant Mine Giant Mine Baker Creek • Existing effluent treatment plant (ETP) • New water treatment plant (WTP) • Effluent quality criteria (EQC) • Aquatic effects monitoring program (AEMP) and other • aquatic monitoring Air quality and greenhouse gas emissions • 2
Bak Baker Creek r Creek Reach 2 Reach 3 Reach 1 Reach 4 Reach 5 Reach 6 Reach 0 3
Baker Creek – Bak r Creek – Risks Risks Flooding Flooding of underground via pits • • Exposure to contamination Exposure to Contamination • • 4
Bak Baker Creek – r Creek – Mitigations itigations Contaminated sediment removal • Floodplain improvements – probable maximum flood • 5
What is the Pr What is the Probable Maximum Flood (PMF)? obable Maximum Flood (PMF)? Flood that comes from the most severe weather that can be imagined Extremely unlikely to happen Reviewer comments ORS 5; YDFKN 21 6
How Do W Ho w Do We Estimat Estimate The PMF? The PMF? Develop estimate for the worst storm that could happen given where the site is located For Baker Creek: Estimated 30cm of rain in 48 hours • Assumed much snow on the ground had fallen • (1 ‐ in ‐ 100 ‐ year snowpack) Roughly the same as assuming the amount of snow and rain • that falls in Yellowknife in one year had fallen in two days on top of a record ‐ year snowpack 7
Bak Baker Creek – r Creek – PMF MF PMF for Baker Creek would be the same as the North Saskatchewan River, in Edmonton, or 5 times the average flow in the Yellowknife River 8
Bak Baker Creek – r Creek – Designed f esigned for the PMF r the PMF Baker Creek will have a channel and a floodplain • Regular flow will be confined to the channel • Extreme floods will flow in the channel and floodplain • Heavy rock protection will be built on the edges of the • floodplain where needed to prevent erosion 9
Int Intervention – ention – Additional F dditional Freeboar eeboard Proponent Position The probable maximum flood is very conservative The Baker Creek design provides protection from even the most extreme flood events Details regarding freeboard for each pit will be provided in the Design Plan Recommendation AN 5 10
Intervener Theme – Int ener Theme – Baker Creek Crit Bak r Creek Criteria and Pr eria and Productivity oductivity Proponent Position Proposed closure activities for Baker Creek will fulfill the promises of the Developer’s Assessment Report Criteria BC 5 ‐ 2 and BC 5 ‐ 3 are under ‐ development and specific to benthics and fish Criteria will be informed by engagement with stakeholders in 2020 and by guidance provided by Fisheries and Oceans Canada through Fisheries Act authorization process GMRP has committed to pre ‐ engagement on all criteria under ‐ development with the Working Group Recommendations CoY 8, YKDFN 2 11
Intervention Bak Int ention Baker Creek and Im r Creek and Impacts t pacts to T Townsit wnsite Area Area Proponent Position Priority must be given to conveying the PMF – alignment is dictated by geometry and topography Impacts to operations to Yellowknife Historical Society will be minimized where possible Recommendations YKHS 3, 4 12
Water T r Treatment eatment 13
Existing Ef Existing Effluent T fluent Treatment Plant eatment Plant Minewater is treated with existing • effluent treatment plant (ETP) built in 1981 Seasonal discharge to Baker Creek • Continued use of the existing ETP for • next several years, no major upgrades proposed A new long ‐ term Water Treatment • Plant (WTP) will be built onsite 14
Existing Effluent Existing Ef fluent Treatment Plant eatment Plant Proposed effluent quality criteria for the ETP • reflect existing treatment technology Reviewer comments incorporated through • water licence process Metal and Diamond Mining Effluent • Regulations (MDMER) limits used to start If past/predicted concentrations were well • below the MDMER limits, EQC lowered New EQC for nitrate, ammonia, sulphate • and chloride From two intervenors: the proposed EQC are • “adequately protective of Baker Creek”, and “the rationales for proposed criteria seem reasonable” 15
New W Ne w Water T r Treatment Plant (W eatment Plant (WTP) TP) A new WTP will be commissioned by approximately 2026 The new plant will: Operate in the central core area of site • Continue to pump from the underground • Discharge year ‐ round to Yellowknife Bay • via nearshore outfall Discharge much lower arsenic than ETP • (10 µg/L compared to 300 µg/L from ETP) 16
Water T r Treatment Plant eatment Plant Proposed a combined mixing • zone (Baker Creek and WTP) One set of water quality • objectives (WQOs) to be met at the edge of the mixing zone • In the future, concentrations expected to: Decrease rapidly with • distance from the breakwater Meet WQOs at the mixing • zone boundary and into Yellowknife Bay 17
Proposed EQC Pr oposed EQC Existing ETP New WTP Parameter Maximum Average Maximum Grab Maximum Average Maximum Grab Concentration Concentration Concentration Concentration 6.5 to 8.5 pH 6.5 to 8.0 TSS, mg/L 15 30 15 30 Sulphate, mg/L 1310 1440 ‐ ‐ Chloride, mg/L 660 720 ‐ ‐ Nitrate, mg ‐ N/L 13 25 13 25 Total Ammonia (variable), mg ‐ N/L pH 6.5 3.1 6.2 10.9 22 Refer to Table 7 in IR Response #06 from Tech Session 2 pH 8.5 0.51 1.0 ‐ ‐ Total antimony, mg/L ‐ ‐ 0.2 0.3 Total arsenic, mg/L 0.3 0.6 0.01 0.02 Total copper, mg/L 0.03 0.06 0.024 0.033 Total lead, mg/L 0.003 0.006 0.003 0.008 Total nickel, mg/L 0.10 0.20 0.10 0.15 Total zinc, mg/L 0.10 0.20 0.08 0.16 Total petroleum hydrocarbons, 3 5 3 5 mg/L Un ‐ ionized ammonia, mg ‐ N/L* 0.5 1.0 0.5 1.0 Radium ‐ 226, Bq/L* 0.37 1.11 0.37 1.11 Cyanide, mg/L* 0.03 0.06 0.5 1 *EQC included only to align with MDMER limits, parameters not identified as COPC 18
Intervener Theme – Int ener Theme – Effluent Crit luent Criteria f eria for W r WTP Proponent Position Effluent quality criteria for chloride and sulphate for water treatment plant are not required • Low discharge volume • High assimilative capacity • Low concentrations of chloride and sulphate at mixing zone boundary (< 10 and 20 mg/L respectively, well below WQOs) In lieu of setting EQC for chloride and sulphate for the WTP: • Monitor influent and effluent • Track against predictions • Report results in Surveillance Network Program and AEMP Recommendations GMOB 13, SEC 10 19
Monit Monitoring ring Monitoring now and in the future will be both: Site ‐ wide • Yellowknife Bay • 20
Site te-Wide W Wate ter M Monito toring Trapper Creek See Standard Operating Procedures for Details SNP 43 ‐ 11 P ‐ LA SNP 43 ‐ 16 Stations, description, project phase, • SNP 43 ‐ 1 rationale, frequency, parameters Pocket Lake Baker ETP Pond discharge Baker Creek Exp Pt Monitoring across the Site—Current and Future Runoff TCAs • • Trapper Creek Sumps • • Pocket Lake Groundwater • • Baker Creek (upper, Mine pool • • middle, lower) ETP/WTP inflow • SNP 43 ‐ 23 (new) Ponds and outflow • SNP 43 ‐ 5 21
Int Intervention – ention – Wat ater Quality Sam er Quality Sampling ling Freq equency of Bak uency of Baker Creek r Creek Proponent Position GMRP does not consider more frequent sampling necessary: • The current water quality sampling regime for Baker Creek downstream of discharge is bi ‐ monthly during the open water season • The ETP discharges seasonally, typically from July to September • The creek freezes to the bottom in many places during the winter Recommendations NSMA 3, 5 22
Int Intervention – ention – Fish and Fish and Benthics Benthics Sampling F Sam ling Freq equency uency Proponent Position GMRP does not consider more frequent sampling necessary: • Effects of existing contamination on Baker Creek are well understood • Frequency is standard for environmental effects monitoring under MDMER and AEMP Recommendation NSMA 5 23
Intervention – Int ention – Monit onitoring Parame oring Parameters Proponent Position The GMRP uses a standard, comprehensive suite of parameters at all water quality monitoring stations. Details are provided in the standard operation procedures Parameters recommended by Alternatives North are already included in the standard suite of parameters Recommendation AN 13 24
Surface W Wate ter M Monito toring • Surveillance network program (SNP) stations • Surface Runoff Stations sampled under operational monitoring program • Details are provided in the standard operating procedures document submitted as part of the GMRP water licence application OMP SNP MDMER/EEM 25
Yello llowknif wknife Ba Bay – y – Special Study pecial Study Existing Conditions Existing Conditions Stations throughout Yellowknife Bay Yellowknife River Near old townsite North Yellowknife Bay Near the proposed outfall Behind and beyond the breakwater Yellowknife Back Bay Near Ndil ǫ Near City Pumphouse 2 Dettah Near Dettah 26
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