OUTS TSTANDING ANDING INFORM ORMATI TION N EFFL FLUEN UENT T - - PowerPoint PPT Presentation

Technical Workshop Snap Lake Mine Final Closure, Water Licence and Land Permit Renewal September 19, 2019

OUTS TSTANDING ANDING INFORM ORMATI TION N EFFL FLUEN UENT T QUALIT ALITY Y CRI RITERI TERIA

PUBLIC LIC PRESEN ENTATION ION

1

• Summary of Updates
• Changes between Version 1 and Version 2 of the linked water quality models (Site, Snap Lake,

Downstream) and effluent quality criteria

• Board IR 1 – Screening Approach
• Board IR 2 – Development of Effluent Quality Criteria and Supporting Evidence
• Board IR 3 – Mixing Zones
• Board IR 4 – Environmental Assessment Measures 1(a) and 1(d)

OUTL TLINE

SUMM MMAR ARY Y OF OF UPD PDATE TES

3

SUMMAR MARY Y OF DIFFE FERENC RENCES BETWE WEEN EN V.1 AND V.2 OF THE EFFLUE UENT QUALI ALITY CRITERIA TERIA REPOR ORT

Time e Pe Period iod Version ion 1 Technic nical al Session

• n

Version ion 2 Before gravity fed collection system 1. Screening process was not completed to identify parameters of potential concern (POPC) 1. Screening process was completed to identify POPC 1. Screening process was updated and completed to identify POPC 2. Mixing zone (1) boundary is 200 m from outfall 2. Mixing zone (1) boundary is 200 m from outfall 2. Mixing zone (1 to 3) boundaries are 200 m from

• utfall

3. Proposed to maintain effluent quality criteria (EQC) from Operations

• 18 parameters

3. Proposed EQC:

• Nitrate
• TSS
• Faecal coliforms
• pH

3. Proposed EQC:

• Nitrate

Same EQC:

• TSS
• Faecal coliforms
• pH

4. Assume modular WTP/RO will be required 4. Assume modular WTP/RO will be required 4. Assume modular WTP/RO will not be required

Change ges s Since nce v1 (in n red)

4

SUMMAR MARY Y OF DIFFE FERENC RENCES BETWE WEEN EN V.1 AND V.2 OF THE EFFLUE UENT QUALI ALITY CRITERIA TERIA REPOR ORT

Time e Pe Period iod Version ion 1 Technic nical al Session

• n

Version ion 2 After gravity fed collection system is established 1. Screening process was completed to identify POPC 1. Screening process was completed to identify POPC 1. Screening process was updated and completed to identify POPC 2. Mixing zone boundaries are 200 m from outfalls 2. Mixing zone boundaries could be as little as 100 m from outfalls 2. Mixing zone boundaries are 200 m from outfalls 3. Proposed EQC:

• Nitrate
• TSS
• pH

3. Proposed EQC:

• Nitrate
• TSS
• pH

3. Proposed EQC:

• Nitrate

Same EQC:

• TSS
• pH

4. Assume passive treatment systems will be required 4. Assume passive treatment systems will be required 4. Assume passive treatment systems will not be required

Change ges s Since nce v1 (in n red)

5

L I N K E D M O D E L S

WATER ER QUALI ALITY MODELS ELS

Water Quantity Model Site Water Quality Model Snap Lake Water Quality Model Downstream Lakes Water Quality Model Effluent Quality Criteria Constructed Wetland Design

No C Chang nges es Since ce v1

6

L I N K E D M O D E L S

SITE E MODEL DEL

Water Quantity Model el Site Water Quality Model Snap Lake Water Quality Model Downstream Lakes Water Quality Model Effluent Quality Criteria Constructed Wetland Design

No C Chang nges es Since ce v1

7

SITE E MODEL DEL - BEFORE ORE GRAVITY FED COLLECTION ECTION SYSTEM EM

Pumping ing Runoff

• ff + Seepage

Seepage

Sump 1 Sump 2 Sump 3 Sump 4 Western Embankment Catchment Water Management Pond Sewage Treatment Plant Underground Mine Snap Lake Modular WTP + RO Unit North Pile Sump 5 Sump 1 Sump 2 Sump 3 Sump 4 Western Embankment Catchment Water Management Pond Sewage Treatment Plant Underground Mine Snap Lake North Pile Sump 5

Ver ersio ion 1 and Tech echnic ical al Session ion Ver ersio ion 2

Change ges s Since nce v1 (in n red)

8

SITE E MODEL DEL - AFTER ER GRAVITY FED COLLECT ECTION ON SYSTEM

Ver ersio ion 1, 1, Technica hnical l Session ion and Ver ersio ion 2

Sump 1 Sump 2 Sump 3 Sump 4 Sump 5 Snap Lake North Pile Western Embankment Catchment

Runoff f + Seepage age Seepage age Outflo low (gravi vity ty)

No C Chang nges es Since ce v1

9

SITE E MODEL DEL PREDICTED DICTED DISCHAR SCHARGES S TO SNAP LAKE

2 4 6 8 10 12 14 16 18 20 22 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 Annual Volume Discahrged to Snap Lake (m3) Millions Year Sump 3 Sump 5 Post-closure

Annual al Disc schar harge ge to Snap p Lake e (m3) Operations (Approved) Before Gravity Fed Collection System After Gravity Fed Collection System >18,000,000 300,000 270,000

No C Chang nges es Since ce v1

2 4 6 8 10 12 14 16 18 20 22 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 Annual Volume Discharged to Snap Lake (m3) Millions Year

Water Treatment Plant Water Management Pond Underground Mine

Operations Closure ECM

10 10

SITE E MODEL DEL ANNUAL AL NITRA TRATE TE LOAD D TO SNAP LAKE

Ver ersio sion 1 and Tec echnical ical Sess ssio ion Annual al Nitrate e Load ad to Snap ap Lake e (kg N/yr) Operations Before Gravity Fed Collection System After Gravity Fed Collection System 90,000 (actual) 250,000 (approved) 5,000 7,000 Ver ersio sion 2 Annual al Nitrate e Load ad to Snap ap Lake e (kg N/yr) Operations Before Gravity Fed Collection System After Gravity Fed Collection System 90,000 (actual) 250,000 (approved) 14,000 16,000

Change ges s Since nce v1 (in n red)

11 11

L I N K E D M O D E L S

SNAP LAKE MODEL EL

Water Quantity Model el Site Water Quality Model Snap Lake Water r Quality Model Downstream Lakes Water Quality Model Effluent Quality Criteria Constructed Wetland Design

No C Chang nges es Since ce v1

12 12

SNAP LA LAKE MODEL EL - BEFORE ORE GRAVIT ITY Y FED COLLECTION ECTION SYSTEM EM

Pumping ing Runoff

• ff

Seepage Outflo low

Change ges s Since nce v1 (in n red)

Natural Runoff Site Runoff North Pile Water Management Pond Downstream Camp Use Underground Mine Modular WTP + RO Unit Sewage Treatment Plant Snap Lake Natural Runoff Site Runoff North Pile Water Management Pond Downstream Camp Use Underground Mine Sewage Treatment Plant Snap Lake

Ver ersio ion 1 and Tech echnic ical al Session ion Ver ersio ion 2

13 13

SNAP LAKE MODEL EL - AFTER ER GRAVITY FED COLLECTI ECTION SYSTEM EM

Natural Runoff Site Runoff North Pile Downstream Sump 5 Outflow Snap Lake Sump 3 Outflow

Runoff Seepage age Outflo low

No C Chang nges es Since ce v1

14 14

L I N K E D M O D E L S

DOWNSTREAM TREAM LAKES MODEL EL

Water Quantity Model el Site Water Quality Model Snap Lake Water Quality Model Downstre ream Lakes es Water er Quality Model Effluent Quality Criteria Constructed Wetland Design

No C Chang nges es Since ce v1

15 15

Snap Lake

DSL1 DSL2 Lac Capot Blanc DSL4 & 5 DSL6 DSL7 DSL8 DSL9/ KING01 DSL10 King Lake King River MacKay Lake Embayment Node 22 Camsell Lake Northeast Lake MacKay Lake West North Lake

DOWNSTREAM TREAM LAKES MODEL EL CONCEP CEPTU TUAL AL DIAGRAM GRAM

DSL - Downstream lake

EXTEN ENDED DED CARE & MAINTENA ENANCE, CE, CLOSURE E AND POST-CL CLOS OSURE No C Chang nges es Since ce v1

Board IR 1

SCREE REENIN NING G AP APPR PROACH CH

17 17

“Clarification and further evidence are required from De Beers on how a single approach to parameter screening is appropriate as well as why these two reasons are no longer applicable to account for uncertainty.”

• In both Version 1 and Version 2 of the EQC Reports, one screening approach was used to

identify parameters of potential concern regardless of the specific discharge source water and discharge locations

• In Version 2 of the EQC Report, the screening process does not use predictions from the

modular water treatment plant /reverse osmosis unit to identify POPC

• Short-term variabilities in water quality concentrations that may occur as a result of

construction and demolition activities have not been accounted for in the site model in Version 1 or Version 2 of the EQC Report

SCREENI EENING PROC OCESS SS TO IDENT ENTIFY FY PARAMETERS ETERS OF POTENT ENTIAL CONCERN CERN

18 18

SCREEN REENING NG PROC OCES ESS TO IDENTI ENTIFY FY PARAM AMETERS ETERS OF POTENTIA TENTIAL L CONC NCERN ERN - BEFOR ORE E GRAVI VITY Y FED COLLE LECTI CTION ON SYSTEM TEM

Ver ersio ion 1 Tech echnic ical l Sessio ion Ver ersio ion 2

Are Predic icted 95th

th P

P WMP Concent ntrat ations ns > Normal al Rang nge in Snap Lake? e? Are Predic icted 95th

th P

P WMP Conce cent ntrat ations ns > AEMP Benchm hmarks? Are Predic icted 95th

th P

P Concent ntratio ions ns at the Mixing ing Zone > 75% of the AEMP Benchm hmark? Water Qualit lity- Based POPC Not a POPC - EQC not Necessary YES YES YES NO NO NO NO NO NO Are Predic icted 95th

th P

P WMP Concent ntrat ations ns > Normal al Rang nge in Snap Lake? e? Are Predic icted 95th

th P

P WMP Concent ntrat ations ns > AEMP Benchm hmarks? Are Predic icted 95th

th P

P Concent ntratio ions ns at the Mixing ing Zone > AEMP Benchm hmark? Water Qualit lity- Based POPC Not a POPC - EQC not Necessary YES YES YES NO NO NO NO NO NO

X

Change ges s Since nce v1 (in n red)

19 19

SCREEN REENING NG PROC OCES ESS TO IDENTI ENTIFY FY PARAM AMETERS ETERS OF POTENTIA TENTIAL L CONC NCERN ERN - AFTER ER GRAVI VITY Y FED D COLL LLECTI ECTION N SYSTEM TEM

Are Predic icted 95th

th P

P Sump 3/Sum ump 5 Concent ntratio ions ns > Normal al Rang nge in Snap Lake? Are Predic icted 95th

th P

P Sump 3/Sum ump 5 Concent ntratio ions ns > AEMP Benchm hmarks? Are Predic icted 95th

th P

P Concent ntratio ions ns at the Mixing ing Zone > 75% of the AEMP Benchm hmark? Water Qualit lity- Based POPC Not a POPC - EQC not Necessary YES YES YES NO NO NO NO NO NO Are Predic icted 95th

th P

P Sump 3/Sum ump 5 Concent ntratio ions ns > Normal al Rang nge in Snap Lake? Are Predic icted 95th

th P

P Sump 3/Sum ump 5 Concent ntratio ions ns > AEMP Benchm hmarks? Are Predic icted 95th

th P

P Concent ntratio ions ns at the Mixing ing Zone > AEMP Benchm hmark? Water Qualit lity- Based POPC Not a POPC - EQC not Necessary YES YES YES NO NO NO NO NO NO

Ver ersio ion 1 and Tech echnic ical al Session ion Ver ersio ion 2

Changes s Since nce v1 (in n red)

Board IR 2

EF EFFL FLUENT ENT QU QUALIT LITY CRITER RITERIA IA AN AND SUPPOR PPORTIN TING G EV EVIDEN DENCE CE

21 21

“Clarification and further evidence are required from De Beers on how this new EQC value was established in the revised EQC Report (Version 2), as well as evidence to support the proposed Nitrate EQC revision as requested in IR 6.”

• The key changes to determine POPC and EQC were:
• Snap Lake modelling was completed assuming that water from the water management

pond, sump 3 and sump 5 was discharged directly to the lake (i.e., no wetland scenario)

• For purposes of the modelling exercise, the modular WTP/RO unit was turned off
• Instead of comparing in-lake predictions to 75% of AEMP benchmarks, in-lake predictions

were compared to 100% of AEMP benchmarks (consistent with the process used in Operations)

• In-lake parameter concentrations are predicted to remain below AEMP benchmarks
• The aquatic ecosystem is protected and water in Snap Lake is safe to drink

EFFLUENT UENT QUALITY CRI RITERI TERIA

22 22

2 4 6 8 10 12 14 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041 2043 2045 2047 2049 Nitrate, as N (mg/L) Year Model Results AEMP Benchmark ECM Closure Post-closure

PREDIC DICTED TED NITRA TRATE TE CONC NCENTRA ENTRATI TIONS NS AT THE HE EDGE OF THE HE EXISTI TING NG MIXIN ING G ZONE IN THE MAIN BASIN SIN OF SNAP LAKE (SNP 02-20E) E)

ECM Closure Post-closure 2 4 6 8 10 12 14 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041 2043 2045 2047 2049 Nitrate, as N (mg/L) Year Model Results AEMP Benchmark 2 4 6 8 10 12 14 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041 2043 2045 2047 2049 Nitrate, as N (mg/L) Year Model Results AEMP Benchmark ECM Closure Post-closure

Version ion 1 Technic nical l Session

• n

Version ion 2

23 23

2 4 6 8 10 12 14 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041 2043 2045 2047 2049 Nitrate, as N (mg/L) Year Model Results AEMP Benchmark ECM Closure Post-closure

PREDIC DICTED TED NITRA TRATE TE CONC NCENTRA ENTRATI TIONS NS AT THE HE EDGE OF THE HE PROPOSE POSED D MIXIN ING G ZONE E IN THE MAIN BASIN OF SNAP LAKE (SNP 02-20H,I)

ECM Closure Post-closure 2 4 6 8 10 12 14 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041 2043 2045 2047 2049 Nitrate, as N (mg/L) Year Model Results AEMP Benchmark 2 4 6 8 10 12 14 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041 2043 2045 2047 2049 Nitrate, as N (mg/L) Year Model Results AEMP Benchmark ECM Closure Post-closure

Version ion 1 Technic nical l Session

• n

Version ion 2

24 24

2 4 6 8 10 12 14 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041 2043 2045 2047 2049 Nitrate, as N (mg/L) Year Model Results AEMP Benchmark ECM Closure Post-closure

PREDIC DICTED TED NITRA TRATE TE CONC NCENTRA ENTRATI TIONS NS AT THE HE EDGE OF THE HE PROPOSE POSED D MIXIN ING G ZONE E IN THE NORTH THWES EST T ARM OF SNAP LAKE (SNP 02-20J,K) J,K)

ECM Closure Post-closure 2 4 6 8 10 12 14 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041 2043 2045 2047 2049 Nitrate, as N (mg/L) Year Model Results AEMP Benchmark

Version ion 1 Technic nical l Session

• n

Version ion 2

2 4 6 8 10 12 14 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041 2043 2045 2047 2049 Nitrate, as N (mg/L) Year Model Results AEMP Benchmark ECM Closure Post-closure

25 25

2 4 6 8 10 12 14 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041 2043 2045 2047 2049 Nitrate, as N (mg/L) Year Model Results AEMP Benchmark ECM Closure Post-closure

PREDICTED DICTED NITRA TRATE TE CONCENT ENTRA RATI TIONS AT THE OUTLET ET OF SNAP LAKE (SNAP0 P08) 8)

ECM Closure Post-closure 2 4 6 8 10 12 14 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041 2043 2045 2047 2049 Nitrate, as N (mg/L) Year Model Results AEMP Benchmark

Version ion 1 Technic nical l Session

• n

Version ion 2

2 4 6 8 10 12 14 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041 2043 2045 2047 2049 Nitrate, as N (mg/L) Year Model Results AEMP Benchmark ECM Closure Post-closure

26 26

SCENARI NARIOS OS TO ESTABL BLISH ISH MAXIM XIMUM UM AVE VERAGE GE CONCENT NCENTRA RATION TION EFFLUENT UENT QUALIT ITY Y CRITER TERIA A FOR R NITRA RATE

Efflue luent SNP 02-20e 20e SNP 02-20h,i ,i SNP 02-20j,k j,k Nitrat rate e (mg-N/L) L) Nitrat rate (mg-N/L) L) AEMP P Benchm hmark ark (mg-N/L) L) Is Nitrat rate e > AEMP P Benchm hmark ark Nitrat rate (mg-N/L) L) AEMP P Benchm hmark ark (mg-N/L) L) Is Nitrat rate e > AEMP P Benchm hmark ark Nitrat rate (mg-N/L) L) AEMP P Benchm hmark ark (mg-N/L) L) Is Nitrat rate e > AEMP P Benchm hmark ark 45 2.1 3.8 No 2.7 4 No 3.7 4.9 No 50 2.3 3.8 No 3.0 4 No 4.1 4.9 No 55 2.4 3.8 No 3.2 4 No 4.4 4.9 No 60 2.6 3.8 No 3.4 4 No 4.8 4.9 No 65 2.8 3.8 No 3.7 4 No 5.2 4.9 Yes EQC Report t V2; Tables les 6-13 to to 6-15 15

27 27

PROPOSE POSED D EFFLUENT UENT QUALIT ITY Y CRIT RITERIA ERIA - BEFORE ORE GRAVIT ITY Y FED COLLECTION ECTION SYSTEM

Change ges s Since nce v1 (in n red)

POPC POPC Units Version ion 1 Tech Sessio ion Version ion 2 MAC MGC MAC MGC MAC MGC Total dissolved solids mg/L 960 1,253

• Total suspended solids

mg/L 7 14 15 25 15 25 Total ammonia, as N mg/L 10 20

• Nitrite, as N

mg/L 0.35 0.6

• Nitrate, as N

mg/L 12 17 25 50 60 80 Total phosphorus, as P mg/L n/a n/a

• Fluoride

mg/L 1.3 2

• Total aluminum

mg/L 0.1 0.2

• Total arsenic

mg/L 0.003 0.01

• Total chromium

mg/L 0.01 0.02

• Total copper

mg/L 0.003 0.01

• Total lead

mg/L 0.01 0.01

• Total nickel

mg/L 0.05 0.1

• Total zinc

mg/L 0.01 0.02

• F1 fraction (C6-C10)

mg/L 4.6 n/a

• F2 fraction (C11-C16)

mg/L 2.1 n/a

• Faecal coliforms

CFU/100 mL 10 20 10 20 10 20 pH

• 6-9

6-9 6-9

28 28

PROPOSE POSED D EFFLUENT UENT QUALIT ITY Y CRIT RITERIA ERIA - AFTER R GRAVIT ITY Y FED COLLECTION ECTION SYSTEM

Change ges s Since nce v1 (in n red) POPC Units ts Version n 1 Tech Sessio sion Versi sion n 2 MAC MGC MAC MGC MAC MGC Total suspended solids mg/L 7 14 15 25 15 25 Nitrate, as N mg/L 12 17 25 50 60 80 pH

• 6-9

6-9 6-9

Board IR 3

MI MIXING ING ZO ZONES NES

30 30

“The 100 m mixing zone has not been accounted for in the response to IR6. Clarification and further evidence are required from De Beers on why the proposed future mixing zone boundaries have remained at 200 m.”

• A near-field mixing model was used to predict dilution factors at 50 m, 100 m, and 150 m

from the approximate locations where the Sump 3 outflow and the Sump 5 outflow will enter Snap Lake

• The predicted dilution factors were used to calculate parameter concentrations in Snap Lake

at 50 m, 100 m, and 150 m from the outfall locations

• Parameter concentrations were compared to proposed Aquatic Effects Monitoring Program

benchmarks

• In V1, parameter concentrations were compared to AEMP benchmarks minus 25%
• In V2, parameter concentrations were compared to AEMP benchmarks

NEAR-FI FIELD D MODEL EL

Change ges s Since nce v1 (in n red)

31 31

NEAR-FI FIELD D MODEL EL NITRA TRATE TE RESUL ULTS TS

Distance nce (m) Lowes west Dilut lution ion Factor ctor Backg ckground

• und Nitrate

ate in Snap p Lake ke (mg (mg-N/L) /L) AEMP P Benchmark (mg (mg-N/L) /L) Pred edict icted ed Nitrate (mg (mg-N/L) /L) Near-field Model 50 18 2.82 5.55 6.00 100 24 4.97 5.21 150 28 4.71 4.86 Snap Lake Model 200

• 3.97

3.44 Distance nce (m) Lowes west Dilut lution ion Factor ctor Backg ckgrou

• und

nd Nitrate e in Snap p Lake ke (mg (mg-N/L) /L) AEMP P Benchmark (mg (mg-N/L) /L) Pred edict icted ed Nitrate (mg (mg-N/L) /L) Near-field Model 50 14 3.67 6.82 7.70 100 18 6.25 6.80 150 21 5.96 6.36 Snap Lake Model 200

• 4.93

4.81

• East Outflow Location in the Main Basin of Snap Lake with an Outflow Concentration of 60 mg-N/L
• West Outflow Location in the Northwest Arm of Snap Lake with an Outflow Concentration of 60 mg-N/L

32 32

• Ver

ersio sion 2

• MAC EQC of 60 mg-N/L for nitrate:
• At 50 m, 100 m, and 150 m, nitrate concentrations were

above 100% of the AEMP benchmark

• At 200 m, nitrate concentrations were below 100% of the

AEMP benchmark

• Proposed mixing zone boundaries in the main basin

and northwest arm of Snap Lake = 200 m

• Tec

echnic ical l Sessio sion

• 95th percentile predicted parameter concentrations

in Sump 3 and Sump 5 outflows:

• At 50 m, concentrations were below 75% of AEMP

benchmarks, except for nitrate and total phosphorus

• At 100 m and 150 m, concentrations were below 75% of

the AEMP benchmarks, except for nitrate

• MAC EQC of 25 mg-N/L for nitrate:
• At 50 m, 100 m, and 150 m, nitrate concentrations were

below 75% of the AEMP benchmark

• Proposed mixing zone boundaries in the main basin

and northwest arm of Snap Lake = 100 m or greater

NEAR-FI FIELD D MODEL EL PREDIC DICTED D CONCENT CENTRA RATION TIONS

Change ges s Since nce v1 (in n red)

Board IR 4

EN ENVI VIRONM ONMENT ENTAL ASSESSMENT ESSMENT ME MEASU ASURE RES S 1(A) (A) AN AND D 1(D (D)

34 34

ENVIRONMENTAL ASSESSMENT SMENT MEASURE SURE 1(A)

• Measure 1(a): The aquatic ecosystem is protected so that fish populations and fish species

composition are not adversely affected compared to pre-mining conditions

• The proposed EQC meet the requirements of Measure 1(a) because parameter concentrations in Snap

Lake are predicted to remain below AEMP benchmarks

35 35

ENVIRONMENTAL ASSESSMENT SMENT MEASURE SURE 1(D)

• Measure 1(d) states that “No Total Dissolved Solids or its constituent ions from Snap Lake

Mine effluent will be detectable, relative to the range of natural variability, at the inlet to MacKay Lake, 44 km downstream of Snap Lake.”

• An Acceptable Limit was established in the Downstream Watercourses Special Study Report (Golder

2017) to assess conformity with Measure 1(d)

• The maximum TDS concentration at Node 22 in MacKay Lake is predicted to remain below the acceptable

limit to meet Measure 1(d) of 19.1 mg/L

Param amet eter er Node e 22 Version ion 1 Version ion 2 Maximum predicted total dissolved solids (mg/L) 18.94 18.95

2 4 6 8 10 12 14 16 18 20 2015 2017 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041 2043 2045 2047 Total dissolved solids (mg/L) Year

Node 22 Model Results Node 22 Monitoring Data Acceptable Limit

36 36

ENVIRONMENTAL ASSESSMENT SMENT MEASURE SURE 1(D), ), CONTINUED TINUED

• Most of the TDS at Node 22 in MacKay Lake can be attributed to historical TDS concentrations

in Snap Lake, which peaked in 2017

100 200 300 400 500 600 2003 2005 2007 2009 2011 2013 2015 2017 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041 2043 2045 2047 2049 Total Disolved Solids (mg/L) Year

Model SNAP08 Monitoring Data

Scena nario rio Inp nput ut TDS (mg/L) L) to to Snap Lake Maximum Predic icted ed TDS (mg/L) L) WMP Sump 3 Sump 5 Node e 22 A 1,141 1,072 904 18.95 B 14.8 14.8 14.8 18.93