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Mapping Complex Pollution Scenarios
Charting Water Flow Along Lenses of Materials with Differing Porosity and Permeability
Challenges of Groundwater Characterization
• The problem is hidden from view
• Operator is limited to what he can measure
• You can only drill so many holes—or can you?
• Geology adds to complication
Challenges of Groundwater Characterization
“When you drill you get a small hole in what may be acres and acres of space,” Gabrielsen said. “You have this spot in time and space you’re looking at and trying to gauge the characteristics of the subsurface. That’s a difficult thing to do.”
---Gabe Gabrielsen
Challenges to Remediate
• How confident are you that the proposed design will fix the problem?
• Are you spending capital with the confidence that it will solve the problem?
• How sure are you that this doesn’t turn into a recurring nightmare?
Challenges to Remediate
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X-ray MRI
•Non-invasive•Great at
showing bones
•Non-invasive•Great at
showing bones
•Non-invasive•Ideal for
showing Soft Tissue detail
•Non-invasive•Ideal for
showing Soft Tissue detail
Which is Best? It Depends…Surgery
•Invasive•Gives you reality of situation
•Invasive•Gives you reality of situation
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Traditional AquaTrack
•Primarily designed for
geologic structure
•Primarily designed for
geologic structure
•Purpose built for mapping
preferential flow paths of water
•Purpose built for mapping
preferential flow paths of water
Purpose-Built Technology has Benefits
• The first hockey mask was used in a Pro game over 100 years after the game was first played
• Technology designed for a specific purpose has inherent benefits
AquaTrack™Controlled Source – Audio Frequency Domain Magnetics
• Direct induction of electricity into groundwater
• Electrical current gathers in conductive features
• Resultant electrical current flow generates magnetic field
• Magnetic field measured on surface of ground using specialized equipment
• Develops three dimensional models of groundwater
WellWell
Well
Bottom of WellBottom of Well
Bottom of Well
Basement Rock
Dry Silts, Sands and Gravels
Power Supply
Antenna Wire
Electrode
Electrode
Magnetic Field Electric Current Flow Lines
Saturated Silts, Sands and Gravels
Typical Electrode Configuration
X component of magnetic field
Y component of magnetic field
Z component of magnetic Field
Coils
GPS Antenna
Portable Computer
Data Logger, GPS Unit Circuit Boards, etc.
“Willowstick”Instrument
Subsurface Electric Current Flow
Magnetic Field
Antenna Wire
Power Supply
Control Panel
CS-AFD-M and Differing Porosities
• Electrical current responds differently to varying porosities- Fractured rock- Sands, gravels- Karst
• Technology does not energize clays- IP effect- Clay acts as electrical
capacitor
CS-AFD-M in Sands and Gravels
WellWell
Well
Bottom of WellBottom of Well
Bottom of Well
Basement Rock
Dry Silts, Sands and Gravels
Power Supply
Antenna Wire
Electrode
Electrode
Magnetic Field Electric Current Flow Lines
Saturated Silts, Sands and Gravels
CS-AFD-M in Silts, Sands and Gravels
CS-AFD-M in Silts, Sands and Gravels
Well
Well
Well
Bottom of Well.
Bottom of Well
Bottom of Well
Basement Rock
Dry Silts, Sands and Gravels
Power Supply
Antenna Wire
Lower Electrode
Upper Electrode
Magnetic Field
Electric Current Flow Lines
Saturated Silts, Sands and Gravels
CS-AFD-M in Silts, Sands and Gravels
CS-AFD-M in Silts, Sands and Gravels
CS-AFD-M in Silts, Sands and Gravels
CS-AFD-M in Silts, Sands and Gravels
CS-AFD-M in Fractured Rock
CS-AFD-M in Karst
Karstic cave found during excavation in right abutment
Right Abutment Grout Curtain
Main Leak(Downstream of Right Abutment)
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Limitations of CS-AFD-M
• Need wells to access groundwater for electrode placement
• Man-made cultural features can interfere with surveys
• Major flows can mask minor flows• Making interpretation of groundwater based
on electrical current flow• Cannot give measure of flow rates
Conclusions
• Technology directly energizes groundwater, maps resultant magnetic field
• Different porosities result in different electrical responses- Can be used to gauge relative porosity and even show areas of
greater permeability
• Technology can be applied to various types of geologic conditions
• A good tool to complement drilling and other traditional characterization methods