Surface Remediation Overview and Key Concerns Surface Remediation - - PowerPoint PPT Presentation

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Surface Remediation Overview and Key Concerns Surface Remediation - - PowerPoint PPT Presentation

Nov 17, 2022 421 likes •994 views

Surface Remediation Overview and Key Concerns Surface Remediation Primary components Baker Creek Tailings and sludge ponds Pits Contaminated soil Buildings and roadways Others Site Overview Site Overview Site

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SLIDE 1

Surface Remediation

Overview and Key Concerns

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SLIDE 2

Surface Remediation

  • Primary components

– Baker Creek – Tailings and sludge ponds – Pits – Contaminated soil – Buildings and roadways – Others

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SLIDE 3

Site Overview

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SLIDE 4

Site Overview

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SLIDE 5

Site Overview

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SLIDE 6

Site Overview

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SLIDE 7

Site Boundary

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SLIDE 8

Baker Creek

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SLIDE 9

Baker Creek

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SLIDE 10

Baker Creek

  • Baker Creek flows through the site

– Enters above Baker Pond and exits into Back Bay

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SLIDE 11

Baker Creek

  • Both “natural” and “constructed” reaches
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SLIDE 12

Baker Creek

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SLIDE 13

Baker Creek

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SLIDE 14

Baker Creek

  • Reach 4 flowed over arsenic stopes

– Relocated and stabilized in 2006

4

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SLIDE 15

Baker Creek

  • Problem sections of Baker Creek in flood

– Narrow diversions above C1 pit and A2 pit

4 1 3

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SLIDE 16

Baker Creek

  • High value habitat

– Reach 4 – Grayling spawning – Reach 6 – Temperature and nutrients

4 1 3 6

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SLIDE 17

Baker Creek

  • Other fish habitat and uses

– Every reach is now known to support some fish uses

4 1 3 6 2 5

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SLIDE 18

Baker Creek

  • Arsenic in sediments – Reach 2, 5, 6

– But other reaches also have areas of contaminated sediments

4 1 3 6 2 5

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SLIDE 19

Baker Creek

  • Water quality

– Arsenic in Baker Creek comes from water treatment plant – And from upstream 220 kg/yr

4 1 3 6 2 5

300 kg/yr

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SLIDE 20

Baker Creek

  • Key Concerns

– Physically impacted in mine area – Water quality – Sediment quality – Concerns for fish, muskrat and humans? – Disturbance from sediment remediation?

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SLIDE 21

Tailings

  • South, Central & North Ponds
  • Northwest Pond
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SLIDE 22

Tailings

  • Foreshore tailings
  • Offshore tailings
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SLIDE 23

Tailings

  • North, Central & South Ponds

– 7M tonnes tailings covering 51 ha – Sludge ponds

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SLIDE 24

Tailings

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SLIDE 25

Tailings

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SLIDE 26

Tailings

  • Seven dams

around Original Impoundments

  • Up to 20 m high
  • Inspected

annually by geotechnical engineer

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SLIDE 27

Tailings

  • Northwest Pond

– 6.5M tonnes tailings covering 44 ha

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SLIDE 28

Tailings

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SLIDE 29

Tailings

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SLIDE 30

Tailings

  • Six dams around

Northwest Pond

  • 15-20 m high
  • Well engineered

and constructed

  • Inspected annually

by geotechnical engineer

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SLIDE 31

Tailings

  • Tailings are fine silty powder
  • About 2,000-4,000 mg/kg arsenic
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SLIDE 32

Tailings

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SLIDE 33

Sludge Ponds

  • Settling pond and polishing pond

– Water treatment residuals

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SLIDE 34

Tailings & Sludge Ponds

  • Key concerns

– Dust – Surface exposure of arsenic – Lack of vegetation – Seepage

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SLIDE 35

Pits

  • Five major pits
  • A2, A1, C1, B2, B1
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SLIDE 36

Pits

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SLIDE 37

Pits

  • Five large pits and three small pits

– Table of pits and volumes

Pit Existing Void Volume1 (m3) Pit Plan Area (m2) A1 757,000 48,000 A2 479,000 32,000 C1 372,000 31,000 B1 331,000 22,000 B2 203,000 20,000 B3 56,000 9,000 B4 10,000 4,000 Brock 10,000 2,000 TOTALS 2,218,000 158,000

1 Volume to spill point elevation

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SLIDE 38

Pits

  • Key concerns

– Safety

  • Steep pit walls are a potential hazard to people
  • Long-term stability of stopes directly below pits
  • Openings to surface

– If Baker Creek channel issues not addressed

  • Flooding could allow water into pits and underground
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SLIDE 39

Contaminated Soils

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SLIDE 40

Contaminated Soils

  • Key concerns

– Land use vs soil contamination levels – Soil quality

  • Human risk

– Inhalation / ingestion – Arsenic uptake by vegetation

  • Wildlife

– Disturbance related to soil remediation?

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SLIDE 41

Buildings

  • Buildings

– In general all buildings on the site will be cleaned and demolished – Five areas with different “issues”

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SLIDE 42

Buildings

  • Townsite Area

– City interested in four Townsite homes

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SLIDE 43

Buildings

  • Townsite and A-Shaft

– NWT Mine Heritage Society interested in Community Hall – A-Shaft is a safety hazard

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SLIDE 44

Buildings

  • Mill Area

– Significant arsenic and asbestos contamination – Requires careful sequence of hazardous material removal, demolition and disposal

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SLIDE 45

Buildings

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SLIDE 46

Buildings

  • Tailings Retreatment,

Effluent Treatment, and Akaitcho Shaft

– Some short-term uses – Then demolition and removal

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SLIDE 47

Buildings

  • Key concerns

– Many remaining buildings contain hazardous materials which could pose risks to workers and environment during demolition if not controlled – Decontamination will generate hazardous wastes requiring safe disposal (either on-site or special facility off-site) – Demolition will generate a large volume of non- hazardous waste requiring on-site disposal

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SLIDE 48

Roadways

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SLIDE 49

Roadways

  • Key concerns

– Some road sections contaminated

  • Mine waste rock containing arsenic

– Some roadways impede site drainage

  • Local flooding problems

– Many roadways not required for future uses

  • Occupied land can be rehabilitated
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SLIDE 50

Other

  • Remediation will create other surface

components

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SLIDE 51

Other

  • Arsenic trioxide management areas
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SLIDE 52

Other

  • Water management system
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SLIDE 53

Other

  • Soil borrow sources
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SLIDE 54

Other

  • Landfill ???
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SLIDE 55

Questions?