LANDFILL MINING TRANSFORMATION

Landfill Mining to transform a former dump into useable land

Chris Sordy (EI Australia) Martin Kelly (Enviropacific)

Landfill Mining to transform a former dump into useable land

1. Context – The site, previous investigations, and approvals 2. RAP 3. Landfill Mining 4. Resource Recovery 5. Post Remediation Monitoring 6. Acknowledgements & Questions

LANDFILL MINING

Overview

1. Context 2. Landfill Mining

3. Gas Assessment 4. Questions

Site Description

Narellan

1. Located in town centre of Narellan NSW

2. Previously Camden Brickworks (c1956-1970)

3. Operated as an unregulated commercial landfill (C&D, manufacturing plastics, glass, cable casings, etc)

4. Closed uncertain late 1980s- early 1990s

5. Remedial requirements:

1. Elevated landfill gas;

2. Elevated landfill contaminant concentrations;

3. Significant Quantity of landfill leachate

Site Investigations 1. 12 investigations over 9 years 2. >5 Site Auditor Reviews 3. Total of 44 monitoring wells 4. Highest CH4 = 85% 5. Characteristic Gas Situations 1 - 5

Residential development is not

recommended on sites CS4 and above

Conceptual Site Model

Remediation Objectives

1. Deliver a site that no longer posed a risk to the community & environment;

2. Maximize the retainment of site suitable materials and limit the offsite disposal to unsuitable materials only.

3. Suitable for a future unconditional proposed residential development.

What is Landfill Mining? Where material that has previously been landfilled is:

1. Excavated 2. Processed 3. Recycled

The Process

Three Stage Process Implemented: Stage 1: Insitu Assessment – separation of site suitable and non suitable material by contaminants; Stage 2: Primary screening of suitable material; Stage 3: Secondary processing (3 phases); Stage 4: Blending and reinstatement; Stage 5: Post completion Landfill Gas (LFG) monitoring.

Stage 1: Insitu Assessment

• Testpit investigation 1 per 80m3; • Visual and laboratory; • 84,000m3 of waste to assess; • Over 30,000 individual analyses; • Assessment for contaminants

and future degradation and gas generation;

• Insitu waste classification per 80m3 cell

Stage 2: Primary Processing • Site Suitable Material

Screened <150mm • Site unsuitable separated into

recyclable (brick, concrete and steel) and non recyclable;

• Non recyclable – offsite disposal;

• Recyclable – crushed onsite for reuse

Stage 3 Secondary Processing

Phase 1 - 40mm Trommel Screen

• Function – Separation of <40mm fines from material

• <40mm – stockpiled; • >40mm – Phase 2

Stage 3 Secondary Processing

Phase 2 – Air Separation Use of Windshifter Technology Function – separation of light and heavy fractions; Light fraction – offsite disposal; Heavy fraction – Phase 3;

Stage 3 Secondary Processing

Phase 3 – Hand Pick Station Function – removal of deleterious material from Heavy Fraction from Phase 2 Hand picked material – offsite disposal

Processing Results

Recovered – 92% Disposed – 8%

40mm Trommel Fines

Air Separator Heavy Fraction

Air Separator Heavy Fraction & Hand Pick Waste

LFG Assessment – Pre Reinstatement • Construction of Trial Bays; • Soil emplaced within the bays and

compacted in accordance with the geotechnical specifications for the final backfill material;

• 2 x vapour points constructed within the trial bays;

• 3 months of LFG monitoring

LFG Assessment – Post Reinstatement • Long Term Monitoring;

• 55 wells installed on site;

• Shallow, deep, and perimeter

locations;

• 10 months of monitoring

• (Spring / Summer / Autumn)

Reinstatement • Recovered material from the

landfill – total 17,000m3;

• Representative of a 92% recovery rate of site suitable materials;

• Recovered material blended with site won ENM clays to increase geophysical strength of material for a deep fill – mitigation of settlement;

0.00%

20.00%

40.00%

60.00%

80.00%

100.00%

0

100

200

300

400

500

600

0.0…

0.03 0.

0…0.

08 0.1…

0.13 0.

1…0.

18 0.2…

0.23 0.

2…0.

28 0.3…

0.33 0.

3…0.

38 M…

Freq

uenc

y

Bin (GSV (Lh-1))

LFG Assessment – Results Maximum GSV = 0.331 Lh-1 (Characteristic Situation 2) 96.79% of results below 0.07 Lh-1 (Characteristic Situation 1) Maximum CH4 = 5% Maximum CO2 = 48.2% All GSV’s driven by CO2

LFG Assessment – Results

CS2

CS1

LFG Assessment – Results

Expected Composition of Landfill Gas

Recorded Results from Monitoring (Round 21)

Conclusion • 92% resource recovery from site suitable materials;

• Majority of gas emissions from the engineered fill were classified as CS1

• ≈ 3% of results marginally in excess of the CS1/CS2 limiting value

• Composition of gas from the site no longer indicates landfill gas generation

• Risk assessment estimates very low ingress of CO2 into future buildings on-site

SITE IS CLASSIFIED AS CHARACTERISTIC SITUATION 1

No further monitoring or gas protection measures within any future development is required

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ACKNOWLEDGEMENT

• The client – Dartwest;

• The site auditor – Rod Harwood (Harwood Enviro)

• All of the site team

• The environmental consultant – EI Australia;

• The geotechnical consultant – Douglas Partners

• The contractor - Enviropacific