Geotechnical and environmental problems—

geophysical methods used to locate mine shafts, construction hazards, leaks, contaminant plumes and other environmental impacts

How to find…

Abandoned Mines

How do I locate the abandoned mine shafts? Where are the surface air shafts? Where is the subsidence going to occur? Where are the rooms, the pillars? Why did the drill-rig kelly drop eight feet?

Best method: Seismic Reflection
May also be applicable: Gravity, GPR

Abandoned Well Casings

Where were the old water wells? Is there pollution getting below the aquatard? How is the pollution getting there? Where are the corroded brine-production casings? Is my building in danger of blowing up from natural gas seepage?

Best method: Magnetics
May also be applicable: Electromagnetics for Metal Detection

Cavities or Voids

Is there a fault and where is it? What is its direction of displacement? How big is the fractured zone around the fault?

Best method: Seismic Refraction
May also be applicable: DC Resistivity, Seismic Reflection

Contaminant Plumes

Is there likely contamination? Where is the location and extent of the contamination plume? How does it decrease in contaminates with distance? Where are the edges of the plume? How is the shape changing with time? How can I reduce my drilling and sampling bill? How can I measure it if I can’t get permission to drill?

Best method: Electromagnetics for Geologic Structures
May also be applicable: GPR, DC Resistivity

Dam, Levee or Reservoir Leaks
(earthen impoundment structure seepage)

Where is the leak? Where is the water flow? Is the flow concentrated or is it sheet flow? How big is the zone that is leaking? How can I get state restrictions on my reservoir’s level removed?

Best method: Self Potential
May also be applicable: DC Resistivity, Electromagnetics for Geologic Structures

Dissolved Salts

Where are the problem areas of salt deposition? How extensive is the salt damage? Why are the plants stunted around that low spot?

Best method: Electromagnetics for Geologic Structure
May also be applicable: DC Resistivity

Fly Ash Locus

What are the limits of the fly ash disposal area? How thick are the deposits? Has any of it migrated downstream? Why is nothing growing here?

Best method: Electromagnetics for Geologic Structures
May also be applicable: DC Resistivity

Landfill Boundaries

Where are the disposal trenches? Where are the edges of the landfill? Where is the leachate going? Where are the larger metallic objects in the landfill? How much do I have to dig up to isolate my uncontrolled landfill? How deep does the slurry wall have to be?

Best method: Electromagnetics for Geologic Structures
May also be applicable: DC Resistivity, Magnetics

Underground Storage Tanks or Drums (USTs)

Where is the tank? Where is the piping for the tank? Where are drums buried? How many tanks and drums are there? Can you prove the tanks have been removed? Are there drums or tanks in this landfill? How do I get a clean Phase II report?

Best method: Time-domain EM
May also be applicable: Magnetics, GPR

Unexploded Ordnance (UXO)

How safe is it to enter this area? How safe is it to dig or drill here? Are there any pieces of metal left on this site? Where are the old bombs? Can I get the Corps of Engineers to pay for cleaning up this area so I can build houses?

Best method: Time-domain EM, NanoTEM®
May also be applicable: Magnetics

Water Quality

What is the water quality at a specific point? How does the TDS vary laterally? Where is the freshwater-brine interface? Where is the plume hiding?

Best method: DC Resistivity
May also be applicable: GPR, Electromagnetics for Geologic Structures, Streaming IP

Water Table

Where is the water table? Does its elevation change when crossing a geologic boundary? Where is the plume? How deep can I make my gravel mine?

Best method: Sesimic Refraction
May also be applicable: DC Resistivity, Electromagnetics for Geologic Structures