Identification of Methane Hazards Near Municipal Landfills Two Australian Case Studies Presented by...

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Identification of Identification of Methane Hazards Near Methane Hazards Near Municipal Landfills Municipal Landfills Two Australian Two Australian Case Studies Case Studies Presented by Manuel Fernandez Environmental Engineer Coffey Geosciences Pty Ltd

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Page 1: Identification of Methane Hazards Near Municipal Landfills Two Australian Case Studies Presented by Manuel Fernandez Environmental Engineer Coffey Geosciences.

Identification of Identification of Methane Hazards Methane Hazards Near Municipal Near Municipal

LandfillsLandfillsTwo Australian Two Australian Case StudiesCase Studies

Presented by Manuel FernandezEnvironmental Engineer

Coffey Geosciences Pty Ltd

Page 2: Identification of Methane Hazards Near Municipal Landfills Two Australian Case Studies Presented by Manuel Fernandez Environmental Engineer Coffey Geosciences.

INTRODUCTIONINTRODUCTION Sydney, NSW (within Australia’s most Sydney, NSW (within Australia’s most

populated state) there is increasing pressure populated state) there is increasing pressure for urban landfor urban land

Land that was once on the fringes of urban Land that was once on the fringes of urban areas is now sought after as prime residential areas is now sought after as prime residential landland

In some cases residents of new developments In some cases residents of new developments are now neighbours with old municipal landfillsare now neighbours with old municipal landfills

Identifying methane hazards is important in the Identifying methane hazards is important in the landfill rehabilitation and land redevelopment landfill rehabilitation and land redevelopment processprocess

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METHANEMETHANE

Colourless, odourless, tasteless gas Sources include swamps, coal/oil mining,

fermentation and landfills Methane (CH4) is flammable and has a

Lower explosive limit of 5% (v/v) Methane can cause oxygen deficient

environments (asphyxiation) and explosion risks

Methane produced in landfills can present a hazard to neighbouring areas

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STUDY LOCATIONSTUDY LOCATION

Study Locations

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CASE STUDY 1CASE STUDY 1 Methane Investigation requested as part of

landfill rehabilitation planning process Explosive concentrations of methane identified

near adjacent residential subdivision Objectives

Assess nature and extent of methane Identify the sources of methane and migration

pathways Provide advice on short term remediation Monitoring Risk Analysis

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AERIAL PHOTOGRAPH OF AERIAL PHOTOGRAPH OF SITESITE

Landfill

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Former Landfill (North)

Oval & Car Park (former sanitary depot)

Residential Residential SubdivisionSubdivision

Wetland

Former Landfill (South)

300m180m

SITE LAYOUT

SewersSewers

Main Drainage LinesMain Drainage Lines

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LandfillSubdivision

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POTENTIAL METHANE POTENTIAL METHANE SOURCESSOURCES

“LANDFILL” Fill Soils

Sanitary waste depot Subdivision fill Backfill around sewers and underground

service trenches Natural organic soils Leaks in natural gas pipelines Deep coal seams

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POTENTIAL METHANE MIGRATION POTENTIAL METHANE MIGRATION PATHWAYS?PATHWAYS?

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INVESTIGATIONS, SHORT TERM INVESTIGATIONS, SHORT TERM

REMEDIATION AND MONITORINGREMEDIATION AND MONITORING Construction of gas venting trench Monitoring inside residential houses Site history study and literature review Geophysical surveys Insitu soil gas testing (724 locations) Logging of Test Pits and Boreholes (44 locations) Installation and sampling of gas and groundwater

wells (66 locations) Gas analysis (fingerprinting) Groundwater Analysis (dissolved methane) Soil Analysis (total organic carbon) Gas pressure testing

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Former Landfill (North)

GAS VENTING TRENCH

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Perforated Pipe

Gravel Filled Trench

Clay Cap

Ventilator

INSTALLATION OF GAS VENTING INSTALLATION OF GAS VENTING

TRENCHTRENCH

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CH4 CH4

Slotted Pipe

Gravel Pack

Concrete and Bentonite Seals

CH4 Meter

TYPICAL GAS WELLTYPICAL GAS WELL

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MAXIMUM CH4 (% BY VOLUME)

0 - 1 .251.25 - 55 - 20>20

INVESTIGATIOINVESTIGATION LOCATIONSN LOCATIONS

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GEOLOGICAL MODELGEOLOGICAL MODEL

Residual clay grading to Patonga claystone

LANDFILL

LANDFILL

Vent Structure

Drain

High methane readings

Channel Alluvium

Dune Sand

High methane readings

Floodplain Alluvium

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RESULTS RESULTS SUBSURFACE METHANE CONCENTRATIONSSUBSURFACE METHANE CONCENTRATIONS

MAXIMUM CH4 (% BY VOLUME)

0 - 1 .251.25 - 55 - 20>20

Max CH4 Conc. (%)

0 – 1.25

1.25 – 5

5 - 20

>20

Methane levels up to 60% in landfill and subdivision

One property recorded 30% methane in a void beneath the concrete slab

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RESULTS RESULTS SUBSURFACE METHANE CONCENTRATIONSSUBSURFACE METHANE CONCENTRATIONS

MAXIMUM CH4 (% BY VOLUME)

0 - 1 .251.25 - 55 - 20>20

Max CH4 Conc. (%)

0 – 1.25

1.25 – 5

5 - 20

>20

Typically, areas that did not have fill recorded low methane concentrations

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IS THE LANDFILL THE SOURCE IS THE LANDFILL THE SOURCE OF METHANE FOUND IN THE OF METHANE FOUND IN THE

SUBDIVISION?SUBDIVISION? Migration through vadose zone (unlikely)

discontinuities in high methane concentrations the north-south drain relatively high water table Fingerprinting - no correlation between gas in landfill and gas in

subdivision Migration Through Service Trenches (unlikely)

similar issues Migration Through Groundwater (unlikely)

Low solubility Concentrations encountered too high for dissolved methane Low pressures

Landfill encroaching into subdivision (unlikely) Site history and aerial photographs do not show landfill

encroaching into the subdivision

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Anecdotal information suggests burial of vegetation and organic soils in the subdivision

Vegetation observed in test pits and Total organic carbon results indicated that the fill and floodplain alluvium have organics (2%-4%)

Conditions beneath the subdivision may be suitable for production of methane

Soccer Oval (Control site) 1.5km away from the landfill in a similar environment shows similar trend with CH4 levels up to 20%.

IS METHANE IN THE SUBDIVISION IS METHANE IN THE SUBDIVISION DERIVED FROM FILL OR NATURAL DERIVED FROM FILL OR NATURAL

ORGANIC SOILS?ORGANIC SOILS?

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Landfill

Soccer Oval (Control Site)

~1.5km

CONTROL SITECONTROL SITE

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WHAT TO BE AWARE OF ?WHAT TO BE AWARE OF ?

No guidance in Australia on naturally produced methane

Soils which could naturally generate methane

Low lying or filled areas Similar site settings

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HOW CAN THIS PROBLEM BE HOW CAN THIS PROBLEM BE MANAGED? MANAGED?

Through the planning process Guidance by regulatory agencies Being aware of the problem Preliminary testing for methane on sites at

risk Methane generating capacity testing Risks Assessment In this case the site was managed through

regulatory control, notation on the land planning certificate and notification to land owners

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CASE STUDY 2CASE STUDY 2

Methane Investigation requested as part of landfill rehabilitation planning process

Relatively new residential subdivision (1999) located near landfill

Investigations concentrated along boundary of landfill adjacent to the subdivision

Study objective were to assess the potential for methane migration from the landfill towards the subdivision

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INVESTIGATION INVESTIGATION TECHNIQUESTECHNIQUES

Site history StudySite history Study Aerial photographsAerial photographs InterviewsInterviews Old site plansOld site plans Council recordsCouncil records

Geophysical (electromagnetic survey)Geophysical (electromagnetic survey) Installation and monitoring from gas Installation and monitoring from gas

wellswells

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1999

Landfill (former quarry)

Residential Subdivision (former quarry)

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1999

Landfill (former quarry)

Residential Subdivision (former quarry)

Sandstone Pillar

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CROSS SECTIONCROSS SECTION

Refuse Waste

Sandstone Pillar

Controlled Fill

House

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Landfill

Subdivision

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1984

Potential Area

of Concern

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Landfill

Residential Subdivision

EM Profile Lines

ELECTROMAGNETIC ELECTROMAGNETIC PROFILE LOCATIONSPROFILE LOCATIONS

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020406080100120140160180200220240260280300320340360380400420440

04812162024283236404448525660646872768084889296100104

020406080100120140160180200220240260280300320340360380400420440

020406080100120140160180200220240260280300320340360380400420440

ELECTROMAGNETIC ELECTROMAGNETIC PROFILE RESULTSPROFILE RESULTS

0 to 5m

5m to 10m

10m to 15m

BOUNDARY

BOUNDARY

BOUNDARY

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GAS WELL LOCATIONSGAS WELL LOCATIONS

Landfill

Residential Subdivision100m

Gas Well

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RESULTSRESULTSCH4 < 0% (v/v) CH4 < 0% (v/v)CH4 up to 44%

(v/v)

REFUSE

Waste encroaches into residential property

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REMEDIATIONREMEDIATION

Short TermShort Term Removal of wastes from rear of residential Removal of wastes from rear of residential

premisespremises Construction of low permeability barrierConstruction of low permeability barrier Ongoing MonitoringOngoing Monitoring

Long TermLong Term Rehabilitation of landfillRehabilitation of landfill Gas collection, venting, flaringGas collection, venting, flaring

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Landfill wastes being excavated from rear of residential properties

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Proximity of properties to landfill wastes

Page 38: Identification of Methane Hazards Near Municipal Landfills Two Australian Case Studies Presented by Manuel Fernandez Environmental Engineer Coffey Geosciences.

CONCLUSIONSCONCLUSIONS Important to establish adequate planning

processes to identify and manage environmental hazards from landfills such as methane prior to redevelopment

Use the right investigation techniques to identify hazards

Be aware of sites that could potentially produce methane through changes to the environment during redevelopment

Methane hazards adjacent to landfills can be managed (barriers, venting, flaring, collection)