ELECTROMAGNETIC INDUCTION EMI In Illinois Soils

Small electrical charge caused by collapse of a magnetic field is introduced into soil Small electrical charge caused by collapse of a magnetic field is introduced into soil Transmitter emits this signal, receiver records the magnitude that moved through the soil Transmitter emits this signal, receiver records the magnitude that moved through the soil Receiver measures resistivity and changes to conductivity Receiver measures resistivity and changes to conductivity Takes a large number of “borings” Takes a large number of “borings”

Soil conductivity is considered to be a soil property Soil conductivity is considered to be a soil property Soil conductivity is influenced by: Soil conductivity is influenced by: moisture content of the soil moisture content of the soil salt or cation content of the soil salt or cation content of the soil amount of clay in the soil amount of clay in the soil type of clay in the soil type of clay in the soil organic matter content of the soil organic matter content of the soil

In Illinois, we have used five different tools In Illinois, we have used five different tools VERIS (Veris Technologies Inc.) VERIS (Veris Technologies Inc.) EM-38 (Geonics Limited) EM-38 (Geonics Limited) EM-31 (Geonics Limited) EM-31 (Geonics Limited) EM-34 (Geonics Limited) EM-34 (Geonics Limited) Dualem (DUALEM Inc.) Dualem (DUALEM Inc.)

EM-31 Illinois NRCS has one of these Illinois NRCS has one of these In operational mode, it is about 10 feet long In operational mode, it is about 10 feet long This separation distance allows for feet of apparent depth penetration This separation distance allows for feet of apparent depth penetration Pedestrian surveys for on-site use and wheeled cart for field use Pedestrian surveys for on-site use and wheeled cart for field use

ILLINOIS USE OF EM-31 Surficial geology interpretations Surficial geology interpretations Assessing permeability differences with depth Assessing permeability differences with depth Separation of soil parent materials Separation of soil parent materials Effluent plumes from animal waste systems Effluent plumes from animal waste systems Salt contamination from oil wells Salt contamination from oil wells Mine land reclamation studies Mine land reclamation studies

Use with updating and refining Order 1 and Order 2 surveys: Use with updating and refining Order 1 and Order 2 surveys: Find small areas of contrasting conductivity Find small areas of contrasting conductivity Fine-tune line placement Fine-tune line placement Assesses broad landscape units quickly Assesses broad landscape units quickly Defines areas needing detailed investigation Defines areas needing detailed investigation