Designation:D6639−01(Reapproved2008)StandardGuideforUsingtheFrequencyDomainElectromagneticMethodforSubsurfaceInvestigations1ThisstandardisissuedunderthefixeddesignationD6639;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1PurposeandApplication:1.1.1Thisguidesummarizestheequipment,fieldprocedures,andinterpretationmethodsfortheassessmentofsubsurfaceconditionsusingthefrequencydomainelectromag-netic(FDEM)method.1.1.2FDEMmeasurementsasdescribedinthisstandardguideareapplicabletomappingsubsurfaceconditionsforgeologic,geotechnical,hydrologic,environmental,agricultural,archaeologicalandforensicinvestigationsaswellasmineralexploration.1.1.3TheFDEMmethodissometimesusedtomapsuchdiversegeologicconditionsasdepthtobedrock,fracturesandfaultzones,voidsandsinkholes,soilandrockproperties,andsalineintrusionaswellasman-inducedenvironmentalcondi-tionsincludingburieddrums,undergroundstoragetanks(USTs),landfillboundariesandconductivegroundwatercon-tamination.1.1.4TheFDEMmethodutilizesthesecondarymagneticfieldinducedintheearthbyatime-varyingprimarymagneticfieldtoexplorethesubsurface.Itmeasurestheamplitudeandphaseoftheinducedfieldatvariousfrequencies.FDEMmeasurementsthereforearedependentontheelectricalprop-ertiesofthesubsurfacesoilandrockorburiedman-madeobjectsaswellastheorientationofanysubsurfacegeologicalfeaturesorman-madeobjects.Inmanycases,theFDEMmeasurementscanbeusedtoidentifythesubsurfacestructureorobject.Thismethodisusedonlywhenitisexpectedthatthesubsurfacesoilorrock,man-madematerialsorgeologicstructurecanbecharacterizedbydifferencesinelectricalconductivity.1.1.5TheFDEMmethodmaybeusedinsteadoftheDirectCurrentResistivitymethod(GuideD6431)whensurfacesoilsareexcessivelyinsulating(forexample,dryorfrozen)oralayerofasphaltorplasticorotherlogisticalconstraintspreventelectr...
