Airborne Geophysical Technology Application

Seeing What Lies Beneath

Airborne electromagnetic (AEM) surveys — originally developed for mineral exploration — can map the spatial extent of metal-contaminated plumes at basin scale. We assessed the feasibility of adapting VTEM and SkyTEM technology for Pilcomayo remediation planning.

VTEM · SkyTEM 500 km Corridor Feasibility Assessment 18–24 Month Estimate

Why Airborne Geophysics?

Beyond Point Sampling

46 fixed monitoring stations provide excellent temporal coverage but sparse spatial resolution. Between stations, contamination patterns are interpolated — and interpolation fails near contamination boundaries, channel bifurcations, and tributary confluences. A single airborne EM survey flight covering 500 km of corridor would generate continuous spatial data at 10–50 m resolution, transforming our understanding of where contamination lies.

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What AEMA geophysical method that maps subsurface electrical conductivity from a low-flying aircraft. Useful for tracing buried contamination plumes and mapping aquifer geometry across long corridors. Can Do — Map the conductivity structure of the upper 10–30 m of alluvium. High conductivity in rivers often correlates with dissolved metal plumes. Low-altitude flights (30–60 m) can resolve the channel and floodplain structure at meaningful spatial scales.

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What AEM Cannot Do — AEM maps electrical conductivity, not metal species. Correlation with ground-truth chemistry is required to convert conductivity anomalies to metal concentration estimates. AEM works best as a gap-filler between monitoring stations, not as a replacement for them. The 3D contamination surfaces on this site are themselves built from interpolated point data at the existing ~18 km station spacing — AEM would densify the input grid that underlies those surfaces.

Platform Options

VTEM vs. SkyTEM

Two proven AEM platforms were assessed for Pilcomayo deployment.

VTEM (Versatile Time Domain EM)

Geotech Ltd. — Primary Recommendation

Proven in South American mining terrains
Excellent depth penetration (30–100 m)
High signal-to-noise in mineralized settings
Established local contractor availability (Bolivia)

Requires helicopter platform (higher mobilization cost)
Less effective over electrically conductive saline water bodies

SkyTEM

SkyTEM Surveys ApS — Alternative Option

Lower altitude capability → higher spatial resolution
Optimized for environmental (shallow) targets
Lighter system — easier logistics in remote areas
Good performance over fresh-water systems

Less established in Bolivia specifically
Shallower investigation depth (~20 m)
More sensitive to cultural noise (power lines, fences)

Three Phases

Deployment Roadmap

3–6 months

Flight Design & GIS Planning

GIS-based flight-line design targeting the highest-priority zones: km 0–100 (Potosí source zone) at 100 m line spacing; km 100–500 (mid-basin) at 200 m spacing. Permits from Bolivia, Argentina, and Paraguay civil aviation authorities. Ground-truth station placement to calibrate conductivity-to-concentration model.

1–2 months

Low-Altitude Survey Flights

Low-altitude flights (30–60 m terrain clearance) over the ~500 km corridor. Approximately 2,500 line-km total. VTEM preferred platform. Simultaneous ground validation sampling at 20 pre-selected stations to build the conductivity-chemistry transfer function.

3–6 months

Data Inversion & Integration

1D/2D inversion of time-domain EM data. Generation of conductivity depth slices at 5, 10, 20, and 30 m depths. Integration with existing 2016–2024 monitoring dataset. Seasonal-transport correlation to identify which conductivity anomalies are persistent vs. seasonally variable. Final plume maps for remediation planning.

Survey Scope

Spatial Coverage and Phasing

A full basin AEM survey would cover ~500 km of the Pilcomayo corridor at 100–200 m line spacing, generating spatial conductivity data at 10–50 m resolution. The current monitoring network averages ~18 km between fixed stations — AEM's value proposition is closing the spatial gap that interpolation between point samples cannot reliably fill, particularly near tributary confluences, channel bifurcations, and source-zone hotspots.

10–30 m

Depth of imaging in alluvium — complementing the surface-only sediment record from existing point sampling

2,500 km

Total flight lines across the full 500 km corridor at recommended spacing

10–50 m

Spatial resolution — vs. ~18 km average spacing between monitoring stations

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Recommendation — A phased deployment beginning with km 0–100 (the Potosí source zone) yields the highest immediate value. This is the reach where the project's analytical findings concentrate — texture-class saturation overrides natural grain-size sorting, the source-to-distal sediment gradient reaches 35×, and all three documented hypoxic events occurred within these stations. Spatial resolution gains in this segment would directly inform the in-situ stabilization recommendations on the Remediation Strategy page.

Connected Pages

Where This Work Connects

AEM survey data would serve two downstream purposes on this project — informing the intervention targeting on the Remediation Strategy page, and densifying the spatial input grid that underlies the 3D contamination surfaces.

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The Intervention Strategy

Remediation Strategy

The in-situ stabilization, phytoremediation, and ex-situ recommendations that AEM spatial data would directly inform — particularly for source-zone targeting in the km 0–100 Potosí reach.

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The Spatial Dataset

3D Contamination Models

Basin-scale contamination surfaces currently built from interpolated point data at ~18 km station spacing — the spatial input grid that an AEM campaign would densify.