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Kingsley Dunham CentreKeyworthNottingham NG12 5GGTel 0115 936 3100© NERC All rights reserved
SiteSite--investigation and landfill investigation and landfill characterisation by airborne geophysicscharacterisation by airborne geophysics
David Beamish
Geological Survey of Finland
British Geological
Survey
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Potential sources of pollutionPotential sources of pollution
migration pathways in the subsurface
source-pathway-receptor model
Why landfills?Why landfills?
Methane emissions and climate changeMethane emissions and climate change
Landfills are main contributor (40%) to UK methane release
Methane is 21 times more powerful than CO2 as a greenhouse gas
They are a significant factor in UK reduced emission targets
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Principally considering subsurface electrical conductivityPrincipally considering subsurface electrical conductivity
It’s a ‘new information’ data set
Ignoring main geological discoveries (regional scale)
Concentrating on environmental information at scale of ~1 to 3 km
Simple mapping information and subsurface volumetric information
OutlineOutline
From geophysical perspective (without technical siteFrom geophysical perspective (without technical site--information)information)
1 active quarry
1 sewage works
5 landfills
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subsurface electrical conductivity depends on:subsurface electrical conductivity depends on:
Pore water geochemistryPore water geochemistry
ionic concentration & mobilityionic concentration & mobility(e.g. Na(e.g. Na++, SO4, SO4--, , ClCl--, K, K++, and NO3, and NO3-- groups)groups)No geochemical discriminationNo geochemical discrimination……it measures only Total Dissolved Solids it measures only Total Dissolved Solids
Pore fluids
Geology
Geology (solid component)Geology (solid component)porosity (i.e. void space)porosity (i.e. void space)mineralogical associations (e.g. clays)mineralogical associations (e.g. clays)
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Flight direction:
Bulk conductivity sampled every ~15m along line
Subsurface volume that contributes to measurement of bulk conductivity
Demonstrating the electromagnetic footprint
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conductivity > 25 mS/m in black
conductivity > 50 mS/m in red
cut at coast
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Study area 2x2 km
Conductivities > 5 mS/m
Yellow = deepest
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Target sewage works (north of Killeter)
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Study area 3x3 km
deeper shallower
Demonstrating low amplitude conductivity mapping (1 to 5)
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Study area 2x2 km
Demonstrating landfill anomaly confined to ~1 flight line
Conductivity > 2 mS/m Magnetic field
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Strabane : Refuse tip adjacent to river Finn/border
Strabane : concrete works
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Study area 3x3 kmDemonstrating landfill anomaly with extensive plume
deeper shallower
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Study area 4x4 km
Demonstrating more extensive landfill anomaly with high conductivity
Power-line monitorconductivity
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Demonstrating volumetric subsurface (to 40 m) information
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Study area 1x1 kmDemonstrating the 3D conductivity distribution
beneath the site
> 80 mS/m
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Demonstrating subsurface conductivities > 55 mS/m (to 30 m )
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Study area 3x2 km
Craigahullier landfill, operating since 1998, occupying a former quarry
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Study area 3x2 kmDemonstrating an engineered landfill in a complex setting
Largest landfill conductivities encountered (young reactive site)
3D perspective view of conductivity
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2 km conductivity cross-section across landfill
Detail. Largest amplitude response (pink contours) and line of cross-section
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Study area 7x7 km
Demonstrating regional scale of saline intrusion and likely geological control
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Study area 1.5x1.5 km
Conceptual hydrogeological flow model
Hightown/Belfast Hills Landfill
(Site Conditioning Plan Report/Site Permit, White Young Green for Macwill Services Ltd)
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Demonstrating conductivity mapping at shallowest frequency
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Demonstrating conductivity iso-surface > 55 mS/m, slices to 80 m depth
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To a degree I’ve have been showing you the data with a view to been showing you the data with a view to addressing the addressing the environmentalenvironmental question:question:
What’s in my back-yard ? Or more correctly….
What’s under my back-yard ?
…..that can be a sensitive question
From a safe perspective, it may be best to treat the airborne data (at the site-scale) as ‘pathfinder’ information
It is ‘new’ information and takes time/effort to digest
The data, inevitably, tend to pose questions that require further understanding and follow-up studies
SummarySummary
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