Water Licence Technical Session March 1 st & 2 nd , 2018 MNML - - PowerPoint PPT Presentation

Con Mine Project Description Water Licence Technical Session March 1st & 2nd, 2018

MNML Introduction

Past

• History of project and environmental compliance

Present

• Site Overview, Status of Reclamation, in place and available technology, variability and

unknowns, Licence term and monitoring requirements. Dwight Grabke, Miramar Northern Mining Ltd. (MNML)

• Existing Conditions Summary (surface water quality and biological), Golder

Future

• Model Framework and predictions, Effluent Quality Criteria (EQC), link to monitoring, Golder
• Proposed Surface and Groundwater Monitoring Program, Golder
• Post-Closure Security Estimate. Dwight Grabke, MNML
• Post-Closure Monitoring, Working Group, Relinquishment. Dwight Grabke, MNML

Project History

1948 1961 1978 2008 2011

1937 Construction

1941 Bluefish Hydro 1952 Acquired Negus Mine 1970 Ceased roasting 1977 Robertson Shaft max depth 1902 m (1712MBSL) 1983-1989 Arsenic Plant in-situ water treatment mid- 80s, WTP in 1987 1992 Autoclave

2003 Mining Ceased

2004 Milling ceased 2007 Closure & Reclamation Plan Approved 2007 Newmont 2010 - 2011 Sludge Processed & Autoclave decommissioned 2015 New WTP 2020 CRP Completed On-going Seasonal WTP 50+years

Reclamation Status

• CRP Nearing Completion
• Approved Covers in Place
• Openings to surface capped
• Structural Demolition

Complete

• Engineered Drainage

Channel Network Complete

• Vegetation Establishing
• Mine workings Continue to

Flood

Effluent Quality History

Old Effluent Treatment Plant

• 1987 to 2010
• Manual operation (labour-intensive)
• Highly variable effluent quality
• Volume of effluent discharged (~1Mm3/year)
• Discharge up to 170 days per year
• As of 2007, no freshwater use for milling

New Effluent Treatment Plant

• New WTP installed in 2015
• Automated operation
• Consistent effluent quality
• Designed to meet Water Licence and MMER limit for

arsenic

• Volume of effluent discharged (<0.2 Mm3/year)
• Discharge up to 50 days per year

Source: Silke (2009)

Receiving Environment History

• Ore produced until mid-2004, then Mine permanently shut-

down

• 2007 all operations ceased
• Treated discharge to the Meg/Keg/Peg Lake water system

since the 1980’s

• In the last 10 years, treated discharge occurred in 2007,

2008, 2010 and then in 2015, 2016, 2017

• The water treatment plant operates seasonally, discharging
• nly during the open-water season
• The location of final discharge is at the southern extremity of

Lower Pud TCA, then drains into a channel that flows into the Meg/Keg/Peg Lake water system

• Enters Great Slave Lake at Jackfish Bay

Remaining Closure Tasks & Data Requirements

Vegetation

Vegetative Island Construction Maintenance Seed and Fertilizer Assessment, Adaptive Management, and Monitoring Acceptance

Minewater

Install Monitoring System Initiate Active Pumping Monitor Response in 3 shafts Establish Monitoring & Management Controls Long-term predictions and end-points for relinquishment

Middle Pud Storage Pond

On-going Water Treatment Complete Shoreline Stabilization Update Survey Data, Storage Curve, Water Balance, PMF/PMP Source water synthetic toxicity analysis study Long-term predictions and end-points for restoring Natural drainage

Receiving Environment Response to Post- Closure Conditions.

Develop monitoring plan for approval Implement monitoring plan yr 1-5 Convene focused working group Review monitoring results Establish realistic expectations for the system

Water Licence Application Summary

• 15 year Water Licence
• Effluent Quality Criteria set to amended MMER
• Lower limits for some parameters (arsenic, nickel, cyanide)
• Addition of unionized ammonia
• Retain pH and hydrocarbons
• Time to monitor, study and evaluate
• Uncertainties in source water chemistry
• Meg-Keg-Peg system (loadings)
• How, when, where the application of water quality objectives in Jackfish Bay
• A reporting framework - focus on state the environment/comparison to triggers for

further monitoring or investigation

• Establishment of a Working Group
• Proposed changes to Surveillance Network Program

Closure

• Closure Plan, nearing completion, anticipated to be

fully complete in 2019-2020.

• Licence term is sufficient to assess performance,

response, and establish long-term objectives for relinquishment

• Some assumptions and uncertainties remain
• MNML is committed to the successful remediation of

the Con Mine Site and will continue to review monitoring/management practices to ensure long- term success.

Insert Flyover video / site tour

Outline

Topics 1, 2

• Receiving Environment History
• Existing Conditions
• Modelling Framework
• Future Conditions
• Proposed EQC

Topics 3, 4

• Monitoring

Topic 5

• Security

Topic 6

• Post-Closure

Water quantity

• Shallow and sometimes dry (e.g., Meg Lake were not sampled in 2015 and 2010 due

to dry conditions) Water quality

• Elevated concentrations of TDS and major ions (e.g., chloride and sulphate), and

some metals (e.g., arsenic and copper) in M-K-P lakes regardless whether discharge is occurring

• Concentrations increase as water flows from Meg to Peg lakes for some parameters

(e.g., for chloride >~1000 mg/L)

• Mixing provided by Jackfish Bay, but concentrations are still above generic CCME

aquatic health guidelines for some parameters (e.g., chloride and arsenic) during periods of no discharge from Con Mine

Receiving Environment – Existing Conditions

Meg and Keg Lakes 2003

Downstream view of unnamed stream entering Meg Lake, May 2003. Downstream view of outlet of Meg Lake entering Keg Lake, 2003

Receiving Environment – Existing Conditions

Meg Lake July 2015 Keg Lake July 2015

• Surface Water Quality - arsenic temporal trend

Receiving Environment – Existing Conditions

2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

Arsenic

• Surface Water Quality - chloride temporal trend

Receiving Environment – Existing Conditions

2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

Chloride

Receiving Environment – 2000 to 2009

Arsenic Chloride

Fish

• Last sampled in 2015
• No major differences between study fish

in Jackfish Bay versus reference areas Benthos

• Last sampled in 2015
• Jackfish Bay was different than reference area
• It had more benthos and some sensitive species

but not as many diverse species

• Contaminated sediment is present in the bay;

methods to account for this were used

Receiving Environment – Existing Conditions

Outlet of Peg Lake Jackfish Bay

Flow

Receiving Environment – Existing Conditions

Benthos (con’t)

• Dry areas in 2015

made sampling challenging

• More work will be

done on benthos in 2018 to confirm why the mid-field area different

Effluent Quality Criteria and Water Quality Management

• Propose setting Effluent Quality Criteria to amended MMER
• lower limits for some parameters (arsenic, nickel, cyanide)
• addition of unionized ammonia
• Retain pH and hydrocarbons
• MNML is not proposing EQC for ions (chloride, sulphate, TDS)
• MNML has investigated waste minimization options for reducing salts.
• RO treatment not a viable option for Con Mine (site-specific conditions) due to:
• Brine waste/concentrates/dust - hazardous
• Substantial power requirements
• Chemical storage
• Scaling, unreliable treatment if influent quality uncertain
• Unintended trade-offs (less metals treatment)
• Transportation of hazardous waste out-of-province (brine, chemicals)

Effluent Quality Criteria

• Are the Water and Effluent Policy Objectives met?
• Based on modelling predictions, MMER limits for metals are protective of water uses

in Jackfish Bay (MVLWB Policy Objective #1)

• MNML proposes the focus be on protection of aquatic life in the far downstream

(i.e., Jackfish Bay) due to the historical loadings of some parameters in the M-K-P system.

• MNML has sought continual minimization of waste (MVLWB Policy Objective #2)
• Constructed a new WTP in 2015
• New WTP designed to meet lower discharge limits in the current Water Licence

MV2007L8-0025, resulted in reduced loadings to the M-K-P lakes system

• Will meet lower amended MMER limits
• RO treatment not a viable option, based on option analysis

Modelling Framework

Developed a modelling framework to simulate concentrations in the receiving environment – existing and future conditions

• PHREEQC, GoldSim and CORMIX
• Calibrated to existing conditions

Modelling Framework

• Calibrated to existing conditions

Modelling Framework

Modelled 5 future scenarios:

• 4 potential effluent scenarios, based on contributions of sources of minewater from

Middle Pud and the three shafts (C1, Negus, and Robertson)

• 1 MMER discharge limit scenario for metals

Predicted water quality in Jackfish Bay:

• Based on median and 95th percentile background water conditions (limited dataset)
• Calculated at 200 and 600 m from inlet of Jackfish Bay – model distances
• Compared to CCME generic guidelines, WQOs, and historical concentrations

Scenario Predicted from PHREEQC MMER Discharge Limits Background Water Quality Case Scenario 1 Scenario 2 Scenario 3 Scenario 4 Scenario 5 Median Predicted Concentrations at 200 and 600 m from the inlet of Jackfish Bay 95th Percentile

Model Results for Jackfish Bay

For all scenarios:

• Substantial mixing in Jackfish Bay
• Generic CCME aquatic life guidelines were met at 200 m

from the inlet of Jackfish Bay for the 95th percentile background case except:

• chloride
• arsenic
• copper

~200 m (12%) ~600 m (3%)

Background and Predicted Concentrations in Jackfish Bay

Background Predicted (Highest Values)

Parameter Median < chronic CCME Median < chronic CCME 95th % < chronic CCME within Historical Range (2007-2017) Median < WQO 95th % < WQO 95th % < acute CCME

Chloride No No Yes Yes No (200 m) Yes (600 m) Yes Arsenic No No Yes Not applicable Copper Yes No (200 m) Yes (600 m) No (200 m) Yes (600 m) No Yes Yes Not applicable

Background = ambient water quality in Jackfish Bay in 2015 (i.e., no WTP discharge has occurred since 2011); Predicted = at 200 and 600 m from the inlet of Jackfish Bay. CCME = CCME water quality guideline for the protection of aquatic life (CCME 1999). WQO = water quality objective for chloride (Elphick 2011) and copper (BCMOE 2017). 95th % = 95th percentile. Refer to Tables 9 to 12 in Effluent Plume Model Technical Memorandum for predicted concentrations and response to Comment MVLWB #1.

Key Messages on EQC/Modelling

• On the basis of the modelling completed to date:
• MMER limits for metals are protective of water uses in Jackfish Bay with

consideration of added loadings through the M-K-P system

• The location of the mixing zone boundary has not yet been determined
• Preliminary testing indicates the quality of the minewater is highly variable with limited

depth-integrated data.

• The proposed EQC for Con Mine are not intended to be the concentrations of

parameters consistently discharged, but rather the maximum concentrations that may be discharged if necessary to allow Con to continue closure activities (minewater management), while still protecting water uses downstream.

Post Closure - Monitoring

Licence Term

• SNP – surface, groundwater, site
• MMER – effluent, receiving, toxicity
• EEM – biological, toxicity
• Meg/Keg/Peg
• Middle Pud
• Minewater
• Vegetation
• Propose Working Group

Longer-term

• SNP/MMER/EEM
• Long-Term monitoring and objectives/criteria from working group for acceptance and

relinquishment

Proposed SNP – Surface Water

• Propose to continue surface water monitoring

(SNP) with modifications:

• Add stations
• 1 station at the inlet of Keg Lake
• 10 SWMP stations on the Con Mine site
• Add parameters
• metals scan at selected SNP stations
• fluoride and reactive silica (internal, short-term)
• Deactivate or remove stations
• Downstream of outfall (SNP 0025-8)
• Reduce monitoring frequency
• arsenic in effluent (use of safe guard analyzer)
• dissolved metals
• parameters below DLs (e.g., organics) or low relative to

water quality guidelines (e.g., radium-226)

• Why?
• more efficient monitoring based on site knowledge
• reduce redundancy and fill in gaps
• alignment with MMER monitoring requirements
• allow for EQC comparisons

Proposed SNP - Groundwater

• Propose to continue groundwater monitoring (SNP) of all active wells,

including dry wells, with the following modifications:

• Groundwater Level – monthly monitoring (no change)
• Groundwater Quality – sampling 2x per year in June and September
• July and August periods consistently produce results that are in the same trend as June and

September.

• Add 5 wells
• 4 in areas without coverage, 1 upgradient well for reference
• Why?
• Document groundwater quality in transition to closure and toward post-closure
• Groundwater plume extent
• Potential effects to receiving water bodies and surface exposure
• Monitor the effects of changing site conditions
• Planning and adaptive management
• Full coverage in place (depth and spatial) for potential future mine flooding above 140 masl.

Minewater Monitoring

Trial Monitoring program during

• bservation Period
• Data loggers in three shafts, Robertson, C1

and Negus at same elevation

• Dedicated SNP sample pumps all three

shafts at same elevation below static pumping

• Real-time monitoring during dewatering
• 7 discrete monitoring points, with 4 for

physical sample collection.

• Provides advanced warning of upward

mixing and lateral influence Management Options:

• Vary pumping rate, schedule, interval, and

location

• Independent/pre-treatment for zinc removal

Surface ~190 masl W/ LTC logger in

• Max. Flooded 140 masl

Active Storage Pump Elevation ~67 masl LTC Logger ~ 67 mbsl SNP Sample Collection Pump ~ 40 masl

Post Closure - Security Estimate

• $7,823,190 currently held as security
• Change to Security to ILOC
• Increased Post-closure by $2.1M
• Discontinue annual review, review and adjust based on

actuals as required on 5 year interval

• Long-term costs discounted at 3% based on 100 year

cost forecast

• WTP based indirect cost relationship curve
• WTP lifecycle maintenance costs added
• Site Maintenance, covered within individual TCAs, and

balance of site

• Annual Geotechnical Inspection and 10 year and DSR
• Long-term monitoring and reporting based on

anticipated effort.