surface geophysical investigation of the areal and vertical extent of metallic waste at the former...

PreparedincooperationwiththeU.S.ArmyCorpsofEngineers,KansasCityDistrict

ScientificInvestigationsReport20045208

SurfaceGeophysicalInvestigationoftheArealandVerticalExtentofMetallicWasteattheFormerTysonValleyPowderFarmnearEureka,Missouri,Spring2004ByLyndsayB.Ball1,WadeH.Kress1,EricD.Anderson2,AndrewP.Teeple1,JamesW.Ferguson3,andCharlesR.Colbert3

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TableofContentsAbstract

Introduction

Methods

ArealExtentofAnomalies

VerticalExtentofAnomalies

SummaryandConclusions

SelectedReferences

Appendix1.GeoreferencedlocationswithinAOC3(table11),AOC7(table...

Appendix21.Graphsrepresentingthetotalpercentfrequencyofoccurrence...



Appendix3.EnvironmentalnoisetestsonA,April21,2004andB,April22,...

Appendix4.Tableshowingcoordinatesofzoneboundaries.

FiguresFigure1.Locationoftheareasofconcern(AOCs),formerTysonValleyPowd...

Figure2a.ResultsoftheelectromagneticandmagneticsurveyatAOC3showi...

Figure2b.Continued.

Figure2c.Continued.

Figure3.SitemapofAOC3showinganomalouszones.

Figure4.PhotographsofsurfacemetalatAOC3includingexposuresofsmal...

Figure5a.ResultsoftheelectromagneticsurveyatAOC7(AandB)andAOC...

Figure5b.Continued.

Figure5c.Continued.

Figure5d.Continued.

Figure6a.ResultsoftheelectromagneticandmagneticsurveyatAOC7show...

Figure6b.Continued.

Figure7.A1andA2,photographsofsurficialmetalinAOC7lookingsouth...


Figure9a.ResultsoftheelectromagneticandmagneticsurveyatAOC10show...

Figure9b.Continued.

Figure10.PhotographsofsurficialscrapmetalinAOC10betweenmark80,...


Figure12.Fielddataofsurveyline1inAOC3.Sectionsshowinginverted...

Figure13.Fielddataofsurveyline2inAOC3.SectionsshowingA,invert...



Figure16.Fielddataofsurveyline5inAOC7.SectionsshowingA,inver...

Figure17.Surveyline1,AOC3.SectionsshowingA,forwardmodel,andinv...

Figure18.Surveyline2,AOC3.SectionsshowingA,forwardmodel,andB,...




Figure22.Sectionshowinginterpretationofinvertedfieldresistivity,in...





Figure27.PhotographstakenduringexcavationactivitiesatA,AOC3,show...

TablesTable11.GeoreferencedlocationswithinAOC3.

Table12.GeoreferencedlocationswithinAOC7.


1U.S.GeologicalSurvey,Lincoln,Nebraska.

2U.S.GeologicalSurvey,Lakewood,Colorado.

3U.S.ArmyCorpsofEngineers,KansasCityDistrict,KansasCity,Missouri.

ConversionFactors,Abbreviations,andDatums

Multiply By ToobtainLengthmeter(m) 3.281 foot(ft)kilometer(km) 0.6214 mile(mi)Areahectare(ha) 0.003861 squaremile(mi2)Volumeliter(L) 2.113 pint(pt)liter(L) 1.057 quart(qt)cubicmeter(m3) 0.2642 gallon(gal)liter(L) 0.9464 cubicinch(in3)

VerticalcoordinateinformationisreferencedtotheNorthAmericanVerticalDatumof1988(NAVD88).

HorizontalcoordinateinformationisreferencedtotheNorthAmericanDatumof1983(NAD83).

Elevation,asusedinthisreport,referstodistanceabovetheverticaldatum.

Abbreviationsusedinthisreport

2DDC resistivitytwodimensionaldirectcurrentresistivityAOC areaofconcernEM electromagneticEMI electromagneticinductionHz hertzkHz kilohertzm metermS/m millisiemenspermeter

mV/V millivoltpervoltnT nanoteslappm partspermillionRTKGPS realtimekinematicglobalpositioningsystemtimedomainIP timedomaininducedpolarizationTRC TysonResearchCenterTVPF TysonValleyPowderFarm

AbstractTheformerTysonValleyPowderFarmnearEureka,Missouri,wasusedprimarilyasastoragefacilityfortheproductionofsmallarmsammunitionduring194147and195161.Asecondaryuseofthesitewasformunitionstestinganddisposal.Surfaceexposuresofsmallarmswaste,characterizedbybrassshellcasingsandfragments,aswellasothermiscellaneousscrapmetalareremnantsofdisposalpracticesthattookplaceduringU.S.Armyoperationandcanbefoundthroughoutthesite.Littlehistoricalinformationexistsdescribingdisposalpractices,andmoredebrisisbelievedtobeburiedinthesubsurface.TheU.S.ArmyCorpsofEngineershasidentifiedseveralareasofconcernthroughouttheformerTysonValleyPowderFarm.AsurfacegeophysicalinvestigationwasperformedbytheU.S.GeologicalSurvey,incooperationwiththeU.S.ArmyCorpsofEngineers,toevaluatethearealandverticalextentofmetallicdebrisinthesubsurfacewithinthreeoftheseareasofconcern.

Electromagneticandmagneticmethodswereusedtolocateanomaliesindicatingrelativelylargeconcentrationsofburiedmetallicdebriswithintheselectedareasofconcern.Mapswerecreatedidentifyingtwelveanomalouszonesinthethreeareasofconcern,andthreeofthesezoneswereselectedforfurtherinvestigation.Theextentanddepthoftheanomalieswithinthesezoneswereexploredusingtwodimensionaldirectcurrentresistivitymethods.Resistivityandtimedomaininducedpolarizationdatawerecomparedtotheanomalouslocationsoftheelectromagneticandmagneticsurveys.

ThegeophysicalmethodsselectedforthisstudywereusefulindeterminingthearealandverticalextentofmetallicwastewithintheformerTysonValleyPowderFarm.However,electromagneticandmagneticmethodswerenotabletodifferentiatemagneticscrapmetalfromnonmagneticmetallicsmallarmswaste,mostlikelyduetothesmallsizeandscattereddistributionofthesmallarmswaste,inadditiontothemixingofbothtypesofdebrisinthesubsurface.

Electromagneticandmagneticdatashowedsomezonesofconcentratedanomalies,whiletherewasageneralscatteringofsmallanomaliesthroughoutthesite.Invertedresistivitysections,aswellasinducedpolarizationsections,showedthedebristohaveamaximumdepthofapproximately1to2metersbelowthesurface.

IntroductionTheformerTysonValleyPowderFarm(TVPF)wasownedandoperatedbytheU.S.Armyfrom194147,andagainfrom195161.TheformerTVPFwasusedprimarilyasastoragefacilityfortheproductionofsmallarmsammunition,althoughmunitionstestinganddisposaltookplaceonthesiteaswell(KringandBailey,2001).DuringU.S.Armyoperation,shellcasings,munitions,munitionscomponents,storagedrums,andmiscellaneousmetallicmaterialsweredisposedofthroughouttheproperty.Duringthesecondphaseofoperationinthe1950's,thesitealsowasusedforthestorageofartilleryroundsandchemicalsusedintracersandincendiarydevices(FrancisZigmundandC.R.Colbert,U.S.ArmyCorpsofEngineers,oralcommun.,2004).However,littlehistoricalinformationexistsdescribingdisposalpracticesduringU.S.Armyoperation.

Aremedialinvestigation(RI)conductedbytheU.S.ArmyCorpsofEngineers(USACE)hasidentifiedseveralareasofconcern(AOCs)forpotentialsoilandwatercontaminationwithintheformerTVPF.SoilsamplesfromAOCs3,7,and10revealedrelativelyelevatedconcentrationsofvarioustraceelements,includingmercuryandarsenic.SurfaceexposuresofshellcasingswerepresentinAOCs3and7,aswellasstoragedrumsandmiscellaneousscrapmetalinAOC10however,thespatialextentanddepthoftheseitemsinthesubsurfacewereunknown.Surfacegeophysicaltechniquesprovideaquick,inexpensive,andnonintrusivemeansofcollectingdatainthesubsurfaceenvironment.Byapplyingelectromagnetic(EM),magnetic,twodimensionaldirectcurrentresistivity(2DDCresistivity),andtimedomaininducedpolarization(timedomainIP)methods,theextentanddepthofanomaliesinthesignalspotentiallyresultingfromburiedmetallicobjectscanbecharacterized.TheU.S.GeologicalSurvey(USGS),incooperationwiththeUSACE,investigatedAOC3,AOC7,andAOC10forsubsurfacemetallicdebrisusingsurfacegeophysicalmethods.TheresultsofthisstudywillaidtheUSACE,KansasCityDistrict,inperformingremovalofmetallicdebrisundertheDefenseEnvironmentalRestorationProgramandinidentifyingpotentiallocationsforgroundwatermonitoringwells.

PurposeandScope

ThisreportdescribestheresultsofEMandmagneticgeophysicalsurveysusedinAOCs3,7,and10withthepurposeofdefiningthearealextentofburiedsmallarmsammunitionwasteandscrapmetal.SelectedanomaliesidentifiedbytheEMandmagneticsurveyswerecharacterizedverticallywith2DDCresistivityandtimedomainIPmethods.Theresultsofexcavationactivitiesarealsopresented,inwhichsomeselectedanomalieswereexcavatedtoassesstheaccuracyofthegeophysicalsurveys.

SiteDescription

TheformerTVPFsiteisinSt.LouisCounty,Missouri.Thesiteisapproximately32kilometerssouthwestoftheCityofSt.Louisand5kilometersnortheastoftheCityofEureka.Thesiteoccupiesapproximately1,060hectaresandisdividedintothreeareas:TysonResearchCenter(TRC),LoneElkCountyPark,andWestTysonCountyPark(KringandBailey,2001)(fig.1).

Figure1.Locationoftheareasofconcern(AOCs),formerTysonValleyPowderFarmnearSt.Louis,Missouri.

AOCs3,7,and10liewithintheTRCproperty,whichiscurrently(2004)ownedandoperatedbyWashingtonUniversityatSt.Louisasabiologicalfieldstation.Thepropertyisapproximately796hectaresinsizeandisboundedonthenorthbytheBurlingtonNorthernRailroadandtheMeramecRiver.Interstate44isthesouthernpropertyboundary.TheeastandwestboundariesoftheTRCareLoneElkParkandWestTysonCountyPark,respectively(EllisEnvironmentalGroup,2003)(fig.1).

AOC3

AOC3,thePoppingKettlearea,covers0.26hectare.ItisnearthenortheasternmostboundaryoftheTRCproperty,andissituatedonthesteeplyslopingforestedhillsideeastofthePoppingKettlebuilding.Asmall,somewhatincisedephemeralstreamflowsthroughthesitenorthwardtowardtheMeramecRiver.Thisareawasprimarilyusedforthedemilitarizationofoffspecificationandchemicallytreated.30and.50caliberammunitionbyuseoflarge,heatedkettles.Moltenprimersandanvilsplusaninorganicslagwereplacedin55gallondrumsand/ordumpedonthegroundatAOC3(FrancisZigmundandC.R.Colbert,U.S.ArmyCorpsofEngineers,oralcommun.,2004).Numerousshellcasingsandrustydrums,bothpartiallyexposedatthesurfaceandburied,havebeenfoundalongandwithinthebanksofthestreamchannel.Allofthedrumsonthesurfacecontainingslag,someofthesmallarmswasteintheupperpartofthecreekbed,andslagpilesadjacenttothePoppingKettlebuildingwereremovedduringaTimeCriticalRemovalAction(TCRA)performedbyAnlabEnvironmentalinNovember1998(U.S.ArmyCorpsofEngineers,2001).Smallarmswastecanstillbefoundinthestreamchannel.

AOC7

AOC7,theLowWaterBridgeOpenDumpSite,isnearthenorthedgeoftheTRCproperty.AOC10isimmediatelynorthofAOC7andformsitsnorthernboundary.ThesouthandeastboundariesofAOC7areborderedbyagravelroad.TysonHollowCreek,anintermittentstream,definesthewesternboundary.Althoughthemajorityofthesiteiscoveredbydeciduousforest,thesoutheasternpartofAOC7isopenandgrassy.Thissitewasusedasadisposalareaforincinerated.30and.50calibersmallarmswaste(HydroGeoLogic,1999).

AOC10

AOC10,theScrapMetalOpenDumpSite,isinaheavilywoodedareadirectlynorthofAOC7andisonaslopinghillside.Theeasternpartofthesiteisanopenfieldthatendsatagravelroad.AOC10isboundedonthenorthbyasmall,unnamedintermittentstream

andtothewestbyTysonHollowCreek.Angleiron,metalcable,metaldrumremnants,andconstructiondebrisareexposedthroughoutthesiteandareconcentratednearTysonHollowCreek.

PreviousInvestigations

AOC3

RelativelyelevatedconcentrationsofmercuryweredetectedintwoshellcasingsandonecompositesoilsamplecollectedfromthestreambedatAOC3in1996bytheUSACE(EllisEnvironmentalGroup,2003).RIswereconductedtodelineatethenatureandextentofcontaminationwithintheTRC.DuringthePhaseIandIIRIs,performedbyHydroGeoLogic,Inc.,soilsampleswerecollectedatmultiplelocations.Sampleanalytesincludedvolatileorganiccompounds(VOCs),semivolatileorganiccompounds(SVOCs),targetanalytelist(TAL)contaminants,explosivesandcyanide.Antimony,arsenic,barium,copper,lead,andzincweredetectedinsamplescollectedfromtheslagdisposalareaatconcentrationsatleastanorderofmagnitudegreaterthanthebackgroundconcentration,withsomelevelsexceedingtheriskbasedconcentration(RBC)(HydroGeoLogic,1999).

AOC7

AOC7alsowasinvestigatedundertheRIs.SoilandgroundwatersampleswerecollectedduringPhaseItoevaluatetheexistenceofcontaminationresultingfromsiteactivities.Traceelementconcentrationsdetectedinthesoilsamplesexceededbackgroundconcentrationsatseverallocations.Theexplosive2,4dinitrotoluene(2,4DNT)wasdetectedinnumeroussurfacesoilsamples.Mercurywasdetectedingroundwatersamplesataconcentrationslightlyabovethemaximumcontaminantlevel(MCL)(HydroGeoLogic,1999).

AdditionalsoilandsedimentsampleswerecollectedduringthePhaseIIIRI,performedbyEllisEnvironmentalGroup,todelineatetheextentofarseniccontamination.Arsenicwasdetectedinsurfacesoil,subsurfacesoil,andstreambedsedimentsamplesatconcentrationsexceedingboththeresidentialandindustrialpreliminaryremediationgoal(PRG).Varioustraceelementsincludingarsenic,chromium,lead,manganese,andmercuryweredetectedatconcentrationsexceedingtheassociatedMCL(EllisEnvironmentalGroup,2003).

AOC10

AOC10alsowasinvestigatedduringthePhaseIIIRI.Surfaceandsubsurfacesoilsampleswereanalyzedforexplosives,VOCs,SVOCs,andarsenic.ArsenicwasdetectedinsubsurfacesoilsamplesatconcentrationsexceedingboththeresidentialandindustrialPRGvalues.Trichloroethene(TCE)wasdetectedingroundwaterataconcentrationexceedingtheMCLforthisconstituent(EllisEnvironmentalGroup,2003).

Hydrogeology

TheformerTVPFischaracterizedbysteepkarsttopography.AccordingtoCriss(2001),thisareaisunderlainbynearly120metersofcarbonatesofPaleozoicageabovetheSt.PeterSandstoneaquifer.ThisdeepaquiferactsasthedominantsourceofpotablewaterfortheTRCaswellasnearbycommunities.Karstfeaturesincludelosingstreamsandlakes,springs,caverns,andsinkholes.ThenearbyMeramecRiverValleycontainsunconsolidateddepositsofgravelandsandthatcomposeashallowaquiferusedbythenearbycommunitiesdownstreamfromtheTVPF(Criss,2001).

TysonHollowCreek,whichactsasthewesternboundaryofAOCs7and10,isunderlainbyapproximately10metersofunconsolidatedalluviumthatoverliestheOrdovicianagedKimmswickLimestone(Criss,2001).Althoughthecreekisintermittentandconsideredtobealosingstream,groundwaterflowallowsdeeperpartsofthecreektoremainwetthroughoutmuchoftheyear.Thechannelsubstrateisdominatedbycoarsesandstocoarsegravelsizedangularchert.TheunnamedstreampassingthroughAOC3isephemeralandhasasubstratesimilartothatofTysonHollowCreek.

Soilsoftheareasofconcerngenerallyarewelldrained.ThedominantsoilseriesinAOC7andAOC10istheElsahSiltLoam,averydeep,welldrainedtosomewhatexcessivelywelldrainedentisolthatoccursinthefloodplainofTysonValleyHollow(Benham,1982).Thereddishbrownalluvialsoiltendstobegravellywithfewtomanyrockfragments.TheFishpotUrbanLandcomplexoccursinthefareasternedgeofAOC7andconsistsofverydeep,somewhatpoorlydrainedalluvialsiltloamsthathavebeendisturbedatleast76centimetersbelowthesurface(Benham,1982).SoilsinAOC3areclassifiedastheMenfroseries.Thesesoilsareverydeep,welldrainedresidualsoilsthatappearonuplandsandbackslopes,aswellasonterracesoftheMissouriandMississippiRiversandtheirtributaries.Thesolumiscomposedofreddishbrownsiltyclayloams,withthetendencytobecomealkalinetowardsthelowerhorizons(NaturalResourceConservationService,2004).

Acknowledgments

TheauthorsacknowledgetheUSACE,KansasCityDistrict,fortheirassistance.AppreciationisalsoextendedtotheUSGSCrustalImagingandCharacterizationTeamforprovidingguidanceandsupportthroughoutthisstudy.SpecialthanksareextendedtothestaffoftheTysonResearchCenter,especiallyDavidLarson,DavidSchilling,andAngeloOldani,forvolunteeringtheirtimeandresources.

MethodsEMandmagneticsurveyswereperformedalonganestablished,georeferencedgridinlateApril2004.Thegridsconsistedofparallellines3metersapartwitheachlinehavingamarkedreferencepositionevery5meters.Alldistancesweremeasuredalongthelandsurfacefollowingthetopographicchanges.AnAshtechZXtremerealtimekinematic(RTK)globalpositioningsystem(GPS)wasusedtogeoreferencethegridsintheopenareasawayfromthetreecanopy,whichinterferedwithsatellitereception(app.1).Gridlocationsunderthetreecanopyweregeoreferencedusinganautomaticlevelandstadiarodwhereconditionsallowed(app.1).Becauseoflineofsightrestrictionsfromtrees,brush,andweatherlimitations,allothergridlocationswereinterpolatedfromgeoreferencedpointsthroughageographicinformationsystem(GIS).Thegridsalsowerereferencedtoexistingpointssuchaspowerpolesfromoverheadutilities,monitoringwells,buildings,andexistingbenchmarks.Locationsofexposedsurfacemetalwererecordedforcomparisontogeophysicaldata.

EMandmagneticmethodswereusedateachAOCtoprovideaninitialevaluationofthearealextentandlocationofanomalies.Thesemethods,whichdonotrequiregroundcontact,canbeperformedwithhandheldinstruments,creatingarelativelyquick,nonintrusivemeansofsurveyingthesubsurfaceenvironmentforburiedmetallicobjects(WonandKeiswetter,1997).EMandmagnetictechniqueswereappliedtoAOCs3,7,and10usingthedeadreckoningtechnique,wherethelinesofthepredeterminedgridwerewalkedanddigitalmarkswereinsertedintothedatasetasthereferencepointsevery5meterswerepassed.Eachdigitalmarkwasthenadjustedtothecorrectreferencepositionduringpostprocessingandthedatabetweenthereferencepositionswereevenlyspaced.

Afterprocessingtheresultsfromtheinitialsurvey,anomaliescommontobothmethodswereidentified.Thedefinitionofan"anomaly"wasdeterminedfromthehistogramsofeachparameterintheresultsofthesurvey(app.2).Themajorityofthevalueswereconsideredbackgroundlevels.Valuesoccurringwithafrequencyintheouter5percentoftotaloccurrencewereclassifiedasanomalies.ZonesweredelineatedaroundspatialgroupingsofanomaliesinAOCs3,7,and10.Thesezonescontainedthemajorityofanomaliesfoundhowever,smaller,isolatedanomaliesdoexistoutsideofthesezones.Selectedzoneswerethenfurtherexploredby2DDCresistivityandtimedomainIPtocharacterizethedepthandarealextentofthevariousanomalies.Excavationofafewfeatureswasperformedimmediatelyfollowingtheresistivitysurveytocomparetheoccurrenceofmetallicdebrisinthesubsurfacetotheinterpretedgeophysicalresults.

ElectromagneticMethods

EMmethodsworkbymeansofelectromagneticinduction(EMI).Atransmittingcoilproducesanelectromagneticfieldthatinducesasecondaryelectromagneticfieldintheground,themagnitudeofwhichisdependentontheconductivityofthesubsurface.Areceivingcoilmeasuresthemagnitudeoftheinducedfieldandcollectsrawinphaseandquadratureresponses.Fromthisrawdata,moreinterpretiveparameterscanbedetermined,suchasmagneticsusceptibilityandapparentelectricalconductivity.TraditionalEMIsensorsarecomposedofseparatetransmittingandreceivingcoilsconnectedbycablesthatrequireprecisechangesincoilspacingtoalterthedepthofmeasurement(skindepth).Incontrast,frequencysoundingmethodsusemultiplefrequenciestoalterskindepth,allowingthespacingofthecoilstobesmallandfixed.Thedevelopmentoffixedcoiltechnologyhasledtocompact,handheldsensorsthatcanbeoperatedbyasingleperson(Won,2003).Becausethesefixedcoilsensorsdonotdemandplatformsorcartsforstabilizationandarecontainedinasingle,lightweightunit,thistypeofEMIsensorwasidealfortheheavilyvegetated,uneventerrainoftheformerTVPF.TheEMpartofthestudywasperformedwiththeGEM2,designedbyGeophex,Ltd.(Geophex,Ltd.,2004).TheGEM2isahandheld,digital,multifrequency,fixedcoilEMIsensorwithabandwidthof300Hertz(Hz)to24kilohertz(kHz).

TheGEM2wasoperatedinfrequencydomainmode,inwhichfivefrequenciesweresimultaneouslytransmittedthroughadigitallysynthesizedwaveform,amethodknownasthepulsewidthmodulationtechnique(Wonandothers,1996).Twobaseperiods,eachbeing1/30ofasecondwhen60Hzisselectedforutilityrelatednoise,wereaveragedforeachmeasurementeventduringthesurvey.Thesensorwasoperatedinverticaldipoleconfiguration.Theverticaldipoleconfigurationistypicallymoreresponsivetosubsurfacemetallicdebrisandhasagreaterdepthofinvestigationthanthehorizontaldipoleconfiguration(Powersandothers,1999).

AnenvironmentalnoisetestwasperformedpriortothebeginningoftheEMsurveytoaidintheselectionofthetransmittingfrequencies(app.3).ThistestwasconductedbyholdingtheGEM2stationaryandcollectingasmalldataset,approximately5secondsinduration.ThedatawerethendownloadedandexaminedfornoiseusingWinGEMversion1.50,apostprocessingsoftwarepackagedesignedbyGeophex,Ltd.,whichcommunicateswiththeGEM2.Frequencieswithhighnoiselevelswereavoided,includingthe60Hzfrequencyassociatedwithoverheadpowerlines.Thefollowingfrequencieswerechosentoobtainavarietyofdepthswhileminimizingharmonicnoise:2,070Hz,5,010Hz,9,030Hz,13,830Hz,and20,010Hz.BecauseofthepresenceofoverheadpowerlinesinAOCs7and10,60Hzwaschosenasamonitoringfrequencythatis,theGEM2didnottransmitthisfrequency,butonlyrecordedtheresponse.AOC7wassurveyedonApril21,2004AOCs3and10weresurveyedonApril22,2004.Theenvironmentalnoisetestwasperformedonbothdays.Theresultsofthetestswerefoundtobesimilar,andthesamefrequencieswereusedforeachAOC(app.3).

AfterEMdatawerecollected,approximatelocalcoordinatevalueswereassignedtoeachmeasurementeventusingWinGEM.Thelocationswerefinalizedinaspreadsheetbasedonthepositioningofthedigitalmarksinthedata.Athreedimensionalgraphicsprogramwasusedtogridrawinphaseandquadratureresultsforeachfrequency,aswellasapparentelectricalconductivityandmagneticsusceptibilityextractedfromtherawdatainWinGEM.Thefinalgriddingwasperformedusingtheminimumcurvaturemethodwithacellsizeof1.25meters.Thegridsweredisplayedbyexaminingthedistributionofdatavaluesandmaximizingthecolorscalethroughoutthemajorityofthevariationsinvalueswhileminimizingtheeffectofextremesingleeventoutliers(app.2).

MagneticMethods

Groundmagneticsurveysconsistofmeasurementsofthetotalmagneticfieldintensityalonggridlines.Oneapproachtogroundmagneticsurveysusestwosensors.Onesensorisusedtocollectthemeasurementsinthegridareawhileanothersensorisusedtomonitorthetimevariationsintheearth'smagneticfieldcausedbymagneticstormsanddiurnalvariations.Postprocessingtechniquesallowfortheremovalofthetimevariationsinthedatacollectedwithinthegridarea.Thustheanomaliesproducedinthepostprocesseddatasetare,becauseoflocalvariationsinthemagneticfield,presumablycausedbysubsurfacematerials(Breiner,1999).Asecondapproach,whichisespeciallyeffectiveforshallow,subsurfaceinvestigations,isthegradienttechnique.Thegradienttechniquemeasuresthedifferenceinthetotalmagneticfieldintensitybetweentwosensorssetatafixeddistanceapartfromeachother.Theanomaliesproducedbythegradienttechniquetendtoresolvecompositeorcomplexanomaliesintotheirindividualcomponents,creatingmoreclearlydefinedanomaliesthanthemoretraditionalmethoddescribedinthefirstapproach(Breiner,1999).Whenusingthegradienttechnique,itisnotnecessarytomonitorandremovethetimevariationsinthemagneticfieldbecausesuchchangeswouldaffectbothsensorsinthesamemanner.Thereforetheanomaliesproducedusingthegradienttechniquereflectonlythemagneticvariationsinthesubsurfacematerials.Becauseofitseffectivenessinshallowinvestigationsanditssimplicity,thegradienttechniquewaschosenforthisstudy,anddatainthisreportarereferredtoasverticalgradient.

TheG858portablecesiummagnetometerfromGeometrics(Geometrics,2004)wasusedtocollectverticalgradientdatathesensorswereoperatedwithonedirectlyovertheother.TheG858hasanoperatingrangefrom17,000nanotesla(nT)to100,000nT.Thetwosensorswerespaced0.76meterapartvertically.Bothsensorsweresettoa15degreeanglefromverticaltomaximizetheintensityofthesignal.Datawerecollectedcontinuouslyat1Hz,oronecyclepersecond,whichgivesasensitivityof0.01nTfor90percentofthereadings.DatawereloggedusingtheMagMappersystemfromGeometrics.

OriginalbinarydataweredownloadedfromtheMagMappersystemandconvertedtoASCIIdatausingMagMap2000softwareprovidedbyGeometrics.Subsequentlythedatawereimportedintoadatabase.Asanaidintheidentificationandremovalofdataspikescausedbybothsaturationofthesensoroverstronglymagneticbodiesandsensororientation,theprofilesoftopsensor,bottomsensor,andverticalgradientwereplottedalongtheyaxis.Thedataspikeswerethendeletedandalinearinterpolationwasperformedtofillinthedeletedvalues.Thedatawerethenplottedinathreedimensionalgraphicsprogramusingminimumcurvaturegriddingmethodwithacellsizeof1.25meters.Theverticalgradientwasdisplayedbyexaminingthedistributionofthedataandmaximizingthecolorscalewithinthepeakoccurringvaluesandminimizingtheeffectofoutliersintheappearanceofthegrid(app.2).

TwoDimensionalDirectCurrentResistivity

UsingthedipoledipoleandWennerSchlumbergerarrays(Loke,2004),directcurrentresistivitymeasurementsweremadebyinducingdirectcurrentintothegroundthroughtwocurrentelectrodesandmeasuringtheresultingvoltagebetweentwopotentialelectrodes.Thedipoledipolearrayisverysensitivetohorizontalchangesinresistivityhowever,itisrelativelyinsensitivetoverticalchangesinresistivity,hasashallowdepthofpenetration,andarelativelylowsignalstrength.TheWennerSchlumbergerarrayhasmoderateresolutioninboththehorizontalandverticaldirections,adeeperpenetrationdepth,andhashighersignalstrengththanthe

dipoledipolearray,resultinginahighersignaltonoiseratio(Loke,2000).Resistancewascalculatedbydividingthemeasuredvoltagebytheinducedcurrent.Theapparentresistivityofthesubsurfacewascalculatedbymultiplyingtheresistancebyageometricfactorthatisdeterminedbythegeometryandthespacingoftheelectrodearray(Stantonandothers,2003).ApparentresistivityfielddatasetswereinvertedusingRES2DINVversion3.52wsoftware(Loke,2003)tocreateinvertedfielddatasetsthatprovideamuchcloserapproximationofthetrueresistivityofthesubsurfacethantherawdataitself.TheinversionprocessisdescribedbyLoke(2004)themodelreferredtointhefollowingquoteisreferredtoastheinvertedfielddatasetinthisreport:

"Ingeophysicalinversion,weseektofindamodelthatgivesaresponsethatissimilartotheactualmeasuredvalues.Themodelisanidealizedmathematicalrepresentationofasectionoftheearth.Themodelhasasetofmodelparametersthatarethephysicalquantitieswewanttoestimatefromtheobserveddata.Themodelresponseisthesyntheticdatathatcanbecalculatedfromthemathematicalrelationshipsdefiningthemodelforagivensetofmodelparameters.Allinversionmethodsessentiallytrytodetermineamodelforthesubsurfacewhoseresponseagreeswiththemeasureddatasubjecttocertainrestrictions.InthecellbasedmethodusedbytheRES2DINVandRES3DINVprograms,themodelparametersaretheresistivityvaluesofthemodelcells,whilethedataisthemeasuredapparentresistivityvalues.Themathematicallinkbetweenthemodelparametersandthemodelresponseforthe2Dand3Dresistivitymodelsisprovidedbythefinitedifferenceorfiniteelementmethods."

Resistivitydatacollectionwasoncearepetitiveprocessinwhichindividual1Dsoundingswerecollectedusingtwocurrentandtwopotentialelectrodes.Thesoundingswerecollectedbykeepingthecenterpointofthearraythesameandincreasingtheelectrodespacingtoobtaininformationaboutdeepersectionsofthesubsurface.Thecenterpointofthearraywasthenmovedandtheprocessrepeateduntilmultiple1Dsoundingswerecollected.Recentadvancesincomputersandequipmentallowtheusertosetupmultipleelectrodesinsuccession(Stantonandothers,2003).Theelectrodesareconnectedtoelectrodetakeoutsbuiltintomulticonductorcablesandjoinedbyanautomaticswitchingunit.Theseunitsaredesignedtoperformautomaticallypredefinedsetsofresistivitymeasurementsusingmultipleelectrodestofacilitaterapiddatacollection(Stantonandothers,2003).ThedataattheformerTVPFsitewerecollectedusinganIRISSyscalR1PlusResistivityMeter.Usingfourelectrodesatatime,theunitswitchesamongacombinationofsixsetsofmulticorecableswithtwelveelectrodeseachat0.5meterspacingtocollectmultiplepointsfromasinglelayout.

TimeDomainInducedPolarization

UsingthedipoledipoleandWennerSchlumbergerarrays(Loke,2004),timedomaininducedpolarization(timedomainIP)measurementsweremadebyinducingdirectcurrentintothegroundthroughtwocurrentelectrodesandmeasuringtheresultingvoltagebetweentwopotentialelectrodes,thenmeasuringtheresidualdecayvoltageindiscretetimeintervalsafterthecurrentisswitchedoff.IntimedomainIPthemeasuredparameter,thechargeability,isgiveninmillivoltpervolt(mV/V).TimedomainIPdatawerecollectedwiththeIRISSyscalR1PlusResistivityMeter.MeasuredchargeabilityfielddatasetswereinvertedusingRES2DINVversion3.52wsoftware(Loke,2003)tocreateinvertedfieldchargeabilitydatasetsthatprovideamuchcloserapproximationofthetruechargeabilityofthesubsurfacethantherawfielddata(Loke,2004).

ForwardModelingofResistivityData

Thepurposeofforwardmodelingistoapproximatelymatchthefieldresistivitydatatoapossiblerepresentationofthesubsurfaceresistivity.Afterexaminationofthefielddata,forwardmodelingwasusedtocalculateapparentresistivityvaluesfromauserspecifiedtwodimensionalgridofrectangularmodelblocks.Themodelblocksaregroupedintolayersthatcorrespondtothelayersfoundintheinvertedfieldresistivitydata.Followingconstruction,theforwardmodelswereusedtocalculateapparentresistivityvalues.TheapparentresistivityvalueswereprocessedusingRES2DINVfollowingthesameproceduresusedinprocessingthefieldresistivitydata.Theforwardmodelwasmodifiedthroughaniterativeprocessinordertomaximizethecorrelationtotheinvertedfieldmodel.Afterprocessing,theinvertedmodelwascomparedtotheinvertedfieldresistivitydataset.Aforwardmodelsolutionisreachedwhentheinvertedmodelandinvertedfieldresistivitydatasetapproximatelymatch.Thefinalforwardmodelgridwasusedtoprovideadetailednonuniqueinterpretationofthesubsurface(Degnanandothers,2001).

AbasicforwardmodelwasdevelopedusingRES2DMODsoftwareversion3.01n(Loke,2002)byestimatingthenumberoflayersidentifiedinthefieldresistivitydata.Driller'slogsfromwellsregisteredwiththeMissouriDepartmentofNaturalResources(URL:http://www.dnr.state.mo.us/geology/geosrv/wellhd/wellhead.htm,accessedMay2004)anddriller'slogsfrompreviousinvestigationswerecomparedtothelayersidentifiedinthefieldresistivitydataandtodeterminethepossiblegeologicdescriptionofeachlayerwithinthebasicmodel.Althoughdriller'slogswereusedforcomparison,thedatawereinsufficienttocreatedetailedgeologicmodels,mostlybecausethewellswithintheAOCswereshallowerthantheresistivitysectionsandthedeepergeologicwellswerenotlocatednearthestudyarea.Becauseofthislackofdetailedgeologicinformation,thefieldresistivitydataweretheprimarydatausedindevelopingtheforwardmodel.

Resistivityvalueswereassignedtoeachlayerbasedonthefieldresistivitydata.Withintheselayers,resistivityvaluescanvarydependingonthecoarsenessandtypeofsediment.Onceeachlayerhadaspecificvalue,themodelwasmodifiedbychangingthedepthandthicknessofthelayer.Aftereachmodification,theforwardmodelwasinvertedandthencomparedtotheinvertedfielddatauntiltheycloselyresembledeachother.Afterthegeneralsizeandshapeofthelayersforeachsurveylineweredeveloped,anomalies,whichmayrepresentmetallicobjects,wereintroducedintotheforwardmodel.Thedepth,size,andshapeofeachanomalywasmodifiedwithintheforwardmodelforeachsurveylineuntiltheinvertedmodelproducedanomaliessimilartoitscorrespondinginvertedfieldresistivitydataset.Aftermodification,thefinalforwardmodelwascomparedtothedriller'slogstoconfirmthatthesolutionisinconcordancewithknowngeologicinformation.

ArealExtentofAnomaliesThearealextentofanomaliespotentiallyindicatingareaswitharelativelylargeabundanceofmetallicdebriswasdeterminedusingEMandmagnetictechniques.Basedontheinitialdata,theverticalgradientwascomparedtothemagneticsusceptibilityat2,070Hzandthetotalapparentelectricalconductivity(EC).Atthelocalscaleofthisstudy,itwasassumedthattherewasnotenoughsignificantgeologicvariationinthenearsurfacetocausenotabledisparitieswithineachindividualAOC.Asthebackgroundgeologicresponsewasassumedtoberelativelyconstant,backgroundvalueswerenotremovedfromtheEMdata.Asaresult,allEMparametervalues,includingmagneticsusceptibilityandtotalapparentEC,wereusedqualitativelyandnotas"true"readings.

FortheEMresultsoftotalapparentECandmagneticsusceptibility,anomalieswerevisualizedashotspotsinorangeandred,representingvalueswithafrequencyofoccurrenceintheupper5percentofthetotalnumberofreadings.Backgroundvaluesfallinthebluerange,whilemoresubtlevariationsareseeninyellowandgreen.Anomaliesintheverticalgradient,aresultofthemagneticsurvey,aredefinedbyapproximatelytheupperandlower5percentofthetotalnumberofreadings.Theremaining90percentoftheverticalgradientdatashowedlittletonogradient.Thisbackgroundrangeisvisualizedbygreen,whileredandbluerepresentpositiveandnegativegradients,respectively.Anomalies,presentinboththeEMandmagneticresults,weregroupedintozonesbasedontheirproximitytooneanother.Anomalieswithrelativelylowintensities,smallsize,orthatwereisolatedweregenerallynotgroupedintozones.Itispossiblethattheseanomaliescharacterizemetallicwastethatexistsoutsideofthezones.

MetallicwastewithintheAOCswasassumedtobemixedbynature,withbothmagneticandnonmagneticmetalsbeingpresentinthesamearea.Althoughthemagnetometerseekstheexistingmagneticfieldofatarget,theEMIsensordetectselectricallyconductive,nonmagneticmetalsaswellasmagnetictargets(WonandKeiswetter,1997).Althoughthisdifferenceinfunctionalitypotentiallyallowsforthedifferentiationbetweenmagneticandnonmagnetictargets,theresultsoftheEMsurveydidnotshowuniqueanomaliesthatwouldbeindicativeofconductive,nonmagnetictargets.Itislikelythatisolated,nonmagneticmetalsdonotexistinconcentration,butarescatteredthroughouttheAOCsinquantitiestoosmalltobedetectedwiththeGEM2.Groundtruthinginformationconfirmedthatwhensmallarmswastewasfound,individualnonmagneticshellcasingswerefounddistributedwithinthesoilmatrix.Becauseofthis,themetalliccompositionofanomalieswasnotabletobedeterminedthroughthisstudy.

Electromagneticandmagneticdatashowedascatteringofanomaliesinallthreeareasofconcern.Anomalouszoneswereidentifiedandmappedzones12inAOC3,zones36inAOC7,andzones711inAOC10(app.4).Gridlocationsareidentifiedbymarkandlinelocation.Forexample,(35,0)referstoapointatmark35online0.

AOC3

Zone1

Theanomaliesinzone1appeartobelocatedinalinearfeatureseenmostclearlyinthemagneticsusceptibilityasthereddiagonalfeaturerunningsouthsoutheastfromabout(35,0)to(50,45)(fig.2B).BasedontheEMandmagneticdata,theanomaliestendtofollowtheephemeralstream(fig.4)however,theanomaliesbegantoshifttowardstheeastbankatlinelocation24andbecameindependentofthestreamatlinelocation39(figs.2and3).Althoughthenorthernpartofthisanomalyzonecouldbeattributedtothemetalpipeandsmallarmswastelocatedintheephemeralstream(figs.3and4),theanomalyintheeastbankismorelikelytobeburiedmetallicobjects.Avisualinvestigationaroundthelocationwheretheanomaliesbegantoshifttowardstheeastbankrevealedapieceofscrapmetalinasmalldepressionat(45,30).Inthisareatheverticalgradientdatashowedanelongatedareaofcloselyspacedhighandlowvalues,suggestingmagnetizationofmetalsinthesubsurface.Theseanomalieswereconsideredsignificantenoughtobefurtherinvestigatedby2DDCresistivity.

Zone2

TheothermajoranomalyofAOC3,locatedat(5,33)andseeninboththemagneticsusceptibilityandverticalgradientdatasets,couldnotbeattributedtoexposedsurfacewaste(fig.2BandC).AlthoughthisanomalywasmuchsmallerintheECresults,azonewasdesignatedaroundthisanomalybasedonthecorrelationbetweenthemagneticsusceptibilityandverticalgradientresults(fig.3).

Figure2a.ResultsoftheelectromagneticandmagneticsurveyatAOC3showingA,totalapparentelectricalconductivityB,magneticsusceptibilityat2,070HzandC,verticalgradient.

Figure2b.ResultsoftheelectromagneticandmagneticsurveyatAOC3showingA,totalapparentelectricalconductivityB,magneticsusceptibilityat2,070HzandC,verticalgradient.

Figure2c.ResultsoftheelectromagneticandmagneticsurveyatAOC3showingA,totalapparentelectricalconductivityB,magneticsusceptibilityat2,070HzandC,verticalgradient.


Figure4a.PhotographsofsurfacemetalatAOC3includingexposuresofsmallarmswasteintheephemeralstreamchannellookingA,northwarddownstream,andB,atthewestbanknearmark40,line12.

Figure4b.PhotographsofsurfacemetalatAOC3includingexposuresofsmallarmswasteintheephemeralstreamchannellookingA,northwarddownstream,andB,atthewestbanknearmark40,line12.

AOC7

AnoverheadpowerlinerunsroughlynorthsouthinthewesternpartofAOC7(fig.8).BecausethepowerlineoversaturatestheGEM2,theEMdatasurroundingthepowerlinemustbeignored.Todeterminewheretheeffectofthepowerlinewasoverpowering,the60Hzmonitoringfrequencywasexamined(fig.5).The60Hzmonitoringfrequencyshowsastrongresponseinanareaofapproximately10metersoneachsideofthepowerline.ThetotalapparentECshowsabandinthesamelocation,indicatingtheneedtomaskoutthissectionoftheAOC.BecauseoftheeffectofthepowerlineontheEMdata,themagnetometersurveywasgiventhemostweightinidentifyingtheanomalies,whiletheEMdatasetswereusedforconfirmation.

Figure5a.ResultsoftheelectromagneticsurveyatAOC7(AandB)andAOC10(CandD)comparingtheinphaseresponseofthe60Hzmonitoringfrequencytothetotalapparentelectricalconductivity.

Figure5b.ResultsoftheelectromagneticsurveyatAOC7(AandB)andAOC10(CandD)comparingtheinphaseresponseofthe60Hzmonitoringfrequencytothetotalapparentelectricalconductivity.

Figure5c.ResultsoftheelectromagneticsurveyatAOC7(AandB)andAOC10(CandD)comparingtheinphaseresponseofthe60Hzmonitoringfrequencytothetotalapparentelectricalconductivity.

Figure5d.ResultsoftheelectromagneticsurveyatAOC7(AandB)andAOC10(CandD)comparingtheinphaseresponseofthe60Hzmonitoringfrequencytothetotalapparentelectricalconductivity.

AnomaliesinAOC7canbeseenintheverticalgradientdatathatarenotfoundtobemajordisturbancesintheEMdata(fig.6).ItshouldbenotedthatmanyoftheseverticalgradientfeaturesoccurintheareainfluencedbythepowerlineswheretheEMmethodwascompromised.Althoughlargesurfaceexposuresofmetallicdebriswerecatalogued,smallerdebrissuchasrandomlydistributedsmallarmswaste,barbedwire,andotherscrapmetalmayhavebeenleftundocumentedunderthedensevegetationthroughoutAOC7.SuchitemscouldhavecausedthescatteredfeaturesfoundintheverticalgradientdatathatweretoosmalltobefoundwiththeEMmethod.

Zone3

Thelargestanomalyoccurredat(40,117)to(5,90)(fig.6).Thisfeatureappearedinboththemagneticsusceptibilityandtheverticalgradient.Thisareawasdocumentedtohavemultiplemetalsheetsonthesurface,aswellasalargedistributionof1inchdiametermetalcable(fig.7).Becauseofthehighlevelofnoisecausedbythelitteringofsurfacemetal,theEMandmagneticsurveyswereunabletodetermineiftherewasmorewasteburiedatthislocation.Therefore,thisanomalywaschosenforfurtherinvestigationwith2DDCresistivity(fig.8).

Zone4

Anotherrelativelylargeanomalyappearedat(5,122),whichwasseeninalltransmittedEMfrequenciesandmagneticdata(fig.6).Atthesurfaceaconcrete"ring"wasfound,approximately4metersindiameter.BecauseofthestrongresponsefromboththeEMandmagneticresults,itwasbelievedthatmetalalsoispresentinthesubsurfaceatthislocation,mostlikelyaspartofthestructuralsupport,suchasrebar(fig.8).

Zone5

Asomewhatlinearanomalyrunningnorthsouth((60,72)to(45,48))canbeseeninalldatasets(fig.6).Althoughpartofthiszonefallswithinthepowerlinecorridor(fig.8),thecorrelationbetweentheverticalgradientandmagneticsusceptibility,inadditiontothemultiplesurfaceexposuresofsmallarmswasteinthisarea(fig.7B),causedthesefeaturestobedelineatedasazone.Smallarmswasteisnotexpectedtocreateastrongresponseintheverticalgradient,astheconcentrationofferrous,ormagnetic,materialsissmallinsuchdebris.Becauseofthestrongresponseshowninfig.6B,itwassuspectedthatmorewastemaybeburiedhereinadditiontothesurfacesmallarmswaste.Thisanomalywasselectedforfurthercharacterizationby2DDCresistivity.

Zone6

Asmallanomalyoccurredinthemagneticsusceptibilityaswellastheverticalgradientnear(20,30)(fig.6).Nosurfacedebriswasrecordedatthislocation.Theclearresponsefrombothinstrumentsvalidatedcreatingazoneforthisfeature(fig.8).

Zone7

Themagneticsusceptibilityof2,070Hzshowsabandoflowintensityanomaliesstartingat(0,39)andextendingto(20,72)(fig.6).However,theverticalgradientdoesnotshowsimilaranomalieswithinthisarea.Datacollectioninthisareawasimpairedbyheavyvegetation,steeptopography,andvehicletrafficonthegravelroadthatbordersAOC7.Althoughthereisthepossibilitythattheanomalyfoundinthemagneticsusceptibilitywascausedbysubsurfacemetals,thedifficultyexperiencedduringdatacollectionandthelackofcorrespondinganomaliesintheverticalgradientresultsinalowerconfidencelevelindelineatingzone7thantheotherzoneswithinAOC7.However,thefeaturesseeninthemagneticsusceptibilityarestrongenoughtobeclassifiedasanomaliesandaredistributedoveranarealargeenoughtowarrantcreatingazoneforthesefeatures.

Figure6a.ResultsoftheelectromagneticandmagneticsurveyatAOC7showingA,magneticsusceptibilityat2,070HzandB,verticalgradient.

Figure6b.ResultsoftheelectromagneticandmagneticsurveyatAOC7showingA,magneticsusceptibilityat2,070HzandB,verticalgradient.

Figure7A1.A1andA2,photographsofsurficialmetalinAOC7lookingsouthbetweenmark40,line117tomark29,line102showing1inchdiametermetalcableandscrapmetal.

Figure7A2.A1andA2,photographsofsurficialmetalinAOC7lookingsouthbetweenmark40,line117tomark29,line102showing1inchdiametermetalcableandscrapmetal.

Figure7B1.B1andB2,photographsofbarbedwireandsmallarmswastenearmark55,line51.

Figure7B2.B1andB2,photographsofbarbedwireandsmallarmswastenearmark55,line51.


AOC10

TheoverheadpowerlinerunningthroughAOC7continuesintoAOC10,causingasimilaroversaturationoftheGEM2withintheareaofinfluence(fig.5).Therefore,theverticalgradientdataweredeterminedtobetheprimaryinvestigationtechnique,whilethemagneticsusceptibilitywasusedasasecondaryparameter.LikeAOC7,therewasanabundanceofscatteredsurfacemetalthroughoutAOC10.Althoughlargedebriswasrecorded,notallsurfacemetalcouldbelocatedanddocumentedbysightbecauseofthevegetativecover.ItispossiblethatthescatteringofsurfacemetalthroughoutAOC10causedthespottyhighandlowvertical

gradientanomalies.

Zone8

Themostintenseanomalieswerefoundat(80,108)to(70,90)(fig.9).Thisareawasscatteredwithexposedsteeldrums,sheetmetal,andotherdebris(fig.10),whicharethelikelycauseoftheseanomalies.Theverticalgradientandmagneticsusceptibilitybothshowedmoresubtleanomaliesextending15meterstotheeast.Thoughthisareaiswithinthepowerlinecorridor,theagreementbetweentheverticalgradientandmagneticsusceptibilitymakeitunlikelythatthesefeaturesaremerelyartifactsofelectricalinterference.Thesesubtlefeaturesweregroupedwiththeresultsoftheexposedmetaltocreatezone8(fig.11).

Zone9

Thesecondmajoranomalyintheverticalgradientdatawaslocatednear(15,30)(fig.9).Scrapmetalwascataloguedonthesurfaceatthislocation.However,thefeaturesshownintheverticalgradientandsubtlyinthemagneticsusceptibilitynorthwardtoline42mayindicateadditionalburiedferrousmetal.Anotherlargeanomalyat(20,51)didnotcorrespondtoasurfaceexposure.Thecorrespondencebetweentheverticalgradientandthemagneticsusceptibilityindicatesthatthislocationislikelytocontainburiedmetal.Subtlemagneticsusceptibilityfeaturessurroundingtheselargeranomaliesfromlinelocation12to60correspondtoanomaliespresentintheverticalgradient.Becauseofthecorrelation,theareabetween(10,12)and(20,66)wasgroupedintozone9.

Zones10,11and12

Zones10,11and12werecreatedaroundsmallanomaliesseeninboththemagneticsusceptibilityandtheverticalgradient.Zone10isdirectlyoverthegravelroadthatrunsalongtheeasternedgeofAOC10andcanbeseenmostclearlyinthemagneticsusceptibilityat(0,102)(fig.9).Despitetheweakerresponseintheverticalgradient,theanomalyseeninthemagneticsusceptibilitywarrantedcreatingasmallzoneforthisfeature.Zones11and12werecreatedaroundsubtlefeaturesseenmostclearlyinthemagneticsusceptibilityat(15,75),and(35,111),respectively(fig.9).AlthoughtheselocationsdidnothaveastrongenoughresponseintheEMmethodtoqualifyasananomaly,thecorrespondingfeaturesintheverticalgradientindicatethatmetalscouldbepresentinthesubsurfacetherefore,azonewascreatedaroundeachofthesefeatures.

Figure9a.ResultsoftheelectromagneticandmagneticsurveyatAOC10showingA,magneticsusceptibilityat2,070HzandB,verticalgradient.

Figure9b.ResultsoftheelectromagneticandmagneticsurveyatAOC10showingA,magneticsusceptibilityat2,070HzandB,verticalgradient.

Figure10a.PhotographsofsurficialscrapmetalinAOC10betweenmark80,line108tomark70,line90.

Figure10b.PhotographsofsurficialscrapmetalinAOC10betweenmark80,line108tomark70,line90.

Figure10c.PhotographsofsurficialscrapmetalinAOC10betweenmark80,line108tomark70,line90.


VerticalExtentofAnomaliesInadditiontodeterminingthearealextentofanomaliesthroughouteachAOC,theverticalextentsweredeterminedforcertainanomaliesinAOCs3and7.Theverticalextentsofselectedanomalieswereanalyzedbyexaminingthe2DDCresistivityandtimedomainIPdata.The2DDCresistivitydatawerecollectedusingadipoledipoleandaWennerSchlumbergerarrayforLine1(fig.3).TimedomainIPmeasurementswerealsocollectedusingthedipoledipolearrayatsurveyline1(fig.12A).Thedatafromeacharraywereinvertedinthefieldandanalyzedtodeterminethemosteffectivearraythatwouldbeusedtocollectdataforadditionalsurveylines.Afterreviewingtherawdataandinversionresultsoftheresistivitydata,theWennerSchlumbergerarray(fig.12B)waschosenforthecollectionofadditionalsurveylines.BoththedipoledipoleandtheWennerSchlumbergerarraysproducedsimilarresultshowever,duetothegeometryofthearray,theWennerSchlumbergerarrayhasalowersignaltonoiseratio,producingthehighestqualitydataforboththerawdataandtheinvertedfieldresistivitydatasets.TheWennerSchlumbergerarraywassubsequentlyusedtocollect2DDCresistivityandtimedomainIPmeasurementsforlines2through5(figs.3and8).TheresultsweredisplayedbyplottingtwodimensionalsectionsoftheinvertedfieldresistivityandinvertedtimedomainIPdatainagradationalcolorscale(figs.12,13,14,15,and16).Thecoolercolorsarelessresistive,orhavealowerchargeability,andthewarmercolorsaremoreresistive,orhaveahigherchargeability.InversionresultsoftheresistivitydataweredisplayedusingalogarithmicscaleandthetimedomainIPinversionresultsaredisplayedusingalinearscaleofchargeabilityvalues.

TheinversionresultsofthefieldresistivitydatafromboththedipoledipoleandWennerSchlumbergerarraysfromsurveyline1(fig.12)andtheWennerSchlumbergerarrayforsurveylines2and3(figs.13and14)wereinterpretedashavingasimilar3unitcasewhereaslines4and5(figs.15and16)weremoredifficulttointerpretbecauseofthenoisecausedbysurfaceandsubsurfacemetallicdebris.Line4wasinterpretedtohavethreeresistivityunitswhereasline5wasinterpretedtohaveonlytworesistivityunits.Unit1isahighresistivityunit(greaterthan74ohmmeters)followedbyunit2,alessresistivelayer(lessthan74ohmmeters).Surveylines1through3alsoshowanoncontinuoushighresistivity(greaterthan74ohmmeters)featurenearthebottomofeachsection,whichisconsideredtobeunit3.Thisunitwasobservedbutitslocationwasnotclearlydefinedbecauseofthereductioninsensitivitynearthebottomofthesection.Sensitivityrepresentsthedegreetowhichachangeintheresistivityofasectionofthesubsurfacewillinfluencethepotentialmeasuredbythearray(Loke,2000).Alterationsinthelocationandpropertiesofunit3inthemodeltendtohavelittleeffectontheinversionresultbecausethebottomandedgesofthesectioninaWennerSchlumbergerarrayistheleastsensitivepartofthesection.Becauseofthislowersensitivity,thecontactsurfaceofunit3isconsideredtobemorepoorlydefinedthanotherunits.Areaswithinunit1thatarelessthan74ohmmetersareconsideredtobeanomaliesandarefoundinsurveylines1,2,4,and5(figs.12,13,15,and16).

SectionsoftheinvertedfieldchargeabilitydatafromtimedomainIPmeasurementsexhibitfeaturesthroughouteachsectionwherechargeabilityincreasesmorethan12mV/Vincomparisonwiththesurroundingregions.Thesefeaturesareconsideredtobeanomaliesforsurveylines1through5(figs.12,13,14,15,and16).Anomaliesoccurringwithinlines1though5aredenotedbythedisplayofcolorsrepresenting12mV/Vorgreater.

TimedomainIPmeasurementsfromsurveylines1,2,and3showedamorefrequentoccurrenceofanomaliesthanwereshowninthefieldresistivitysections(figs.12,13,and14).Thelackoflowresistivityanomaliesshownintheresistivitysectionsofsurveylines1,2and3couldpossiblybeexplainedbyarelativelyhighconcentrationofhighlyresistivechertfragmentsinunit1,aswellasthescattereddistributionofsmallarmswastethroughoutthesoilmatrixdiscoveredduringexcavationactivities.Thechertcouldbeactingasaninsulator,maskingthelessresistiveinclusionsofsmallarmswaste.However,achargecouldstillbeinducedintheisolatedsmallarmswaste,causingagreaterIPresponsethanthesurroundingtopsoilandchertfragments.

Surveylines4and5showlarge,lowresistivityanomaliesthroughouttheresistivityandtimedomainIPsections(figs.15and16).Theselowresistivityanomaliescouldbeattributedtobarbedwire(fig.7B)foundalongsurveyline4and1inchdiametermetalcable(fig.7A)foundalongsurveyline5.Thepresenceofthissurficialmetalcouldhavecreatedpreferentialelectricalconduitsnearthesurface,causingthemajorityofthecurrenttransmittedbythecurrentelectrodestoreachthepotentialelectrodeswithouttravelingthroughthemoreresistivesubsurfacegeology.Theinversionprocesswouldhaveprojectedtheselowresistivity,surfaceinfluencedreadingsatfalsedepths,creatinglarge,deepanomaliesinthesubsurface.

Figure12a.Fielddataofsurveyline1inAOC3.Sectionsshowinginvertedtwodimensional,directcurrentresistivitydatausingA,adipoledipolearray,B,aWennerSchlumbergerarray,andC,invertedtimedomaininducedpolarizationdatausingadipoledipolearray.

Figure12b.Fielddataofsurveyline1inAOC3.Sectionsshowinginvertedtwodimensional,directcurrentresistivitydatausingA,adipoledipolearray,B,aWennerSchlumbergerarray,andC,invertedtimedomaininducedpolarizationdatausingadipoledipolearray.

Figure12c.Fielddataofsurveyline1inAOC3.Sectionsshowinginvertedtwodimensional,directcurrentresistivitydatausingA,adipoledipolearray,B,aWennerSchlumbergerarray,andC,invertedtimedomaininducedpolarizationdatausingadipoledipolearray.

Figure13a.Fielddataofsurveyline2inAOC3.SectionsshowingA,invertedtwodimensional,directcurrentresistivitydatausingaWennerSchlumbergerarray,andB,invertedtimedomaininducedpolarizationdatausingadipoledipolearray.

Figure13b.Fielddataofsurveyline2inAOC3.SectionsshowingA,invertedtwodimensional,directcurrentresistivitydatausingaWennerSchlumbergerarray,andB,invertedtimedomaininducedpolarizationdatausingadipoledipolearray.




ForwardModelData

Afterthefielddatawereexamined,forwardmodelswerecreatedfor2DDCresistivitysurveylines1through5.Thelayersusedinforwardmodelingwereassignedresistivityvaluesbasedonthefieldresistivitydatasetandwerealteredaccordingtotheresultsofthemodelinversion.Geologicdescriptionsweregiventoeachlayerbasedondriller'slogs:aresistivityof250ohmmeterswasusedtomodelthetopsoilwithchertfragmentsinlayer1,aresistivityof25ohmmeterswasusedtomodeltheclayinlayer2,andaresistivityof250ohmmeterswasusedtomodelthelimestoneinlayer3.Layer1containsareasthatrangeinresistivity,believedtoresultfromvariationsintheabundanceofchertfragmentswithinthetopsoil.Therefore,someareasinlayer1weremodeledwithvalueslessthan250ohmmeters.Valuesof50and100ohmmeterswereusedtorepresentareasoflayer1wheretherewasa

decreaseinresistivity.Insurveyline3,layer1alsocontainedareaswhereresistivityvaluesincreased(fig.14).Thisareawaslocatedalonganunnamedephemeralstream(fig.3)inAOC3andwasassociatedwithanincreaseintheabundanceofgravelandcobblesizedchert,whichwasassignedaresistivityof750ohmmeters.Surveyline4inAOC7,nearTysonHollowCreek(fig.8),alsohadanincreaseinresistivityinlayer1becauseofgravelandcobblesizedchert.Avalueof1,000ohmmeterswasusedinlayer1toindicatetheareawhereresistivityincreased,whichisalsoconsideredtoreflectanincreaseintheabundanceofgravelandcobblesizedchertdeposits.Lowresistivityanomaliesintheinvertedfieldresistivitydatafromsurveylines1,2,and5wereassignedaresistivityof10ohmmetersintheforwardmodelsforeachline.Line4alsocontainedlowresistivityanomaliesappearinginlayer1however,toproduceaninvertedmodelresistivitysectionthatcloselycorrespondedwiththeinvertedfieldresistivitydatafromline4,aresistivityof0.5ohmmeterwasusedinthemodelingofanomaliesforsurveyline4.

Line1forwardmodel(fig.17A)wasusedastheinitialinputmodelgridforlines2through5.Aftermanyiterations,athreelayermodelconsistingoftopsoilwithchertfragments(layer1),clay(layer2),andlimestone(layer3)wasproducedforlines1,2,3and4(figs.17A,18A,19A,and20A).Atwolayermodelconsistingoftopsoilwithchertfragments(layer1)andclay(layer2)wasdevelopedforsurveyline5inAOC7(fig.21A).Amodelsolutionwasreachedwhentheinversionresultsofthemodel(figs.17C,18B,19B,20B,and21B)visuallyresembledtheinversionresultsfromthefielddata(figs.12B,13A,14A,15A,16A).

Figure17a.Surveyline1,AOC3.SectionsshowingA,forwardmodel,andinvertedmodelresistivitydatausingB,adipoledipolearrayandC,aWennerSchlumbergerarrayfromtheforwardmodel.

Figure17b.Surveyline1,AOC3.SectionsshowingA,forwardmodel,andinvertedmodelresistivitydatausingB,adipoledipolearrayandC,aWennerSchlumbergerarrayfromtheforwardmodel.

Figure17c.Surveyline1,AOC3.SectionsshowingA,forwardmodel,andinvertedmodelresistivitydatausingB,adipoledipolearrayandC,aWennerSchlumbergerarrayfromtheforwardmodel.

Figure18a.Surveyline2,AOC3.SectionsshowingA,forwardmodel,andB,invertedmodelresistivitydatausingaWennerSchlumbergerarrayfromtheforwardmodel.

Figure18b.Surveyline2,AOC3.SectionsshowingA,forwardmodel,andB,invertedmodelresistivitydatausingaWennerSchlumbergerarrayfromtheforwardmodel.




InterpretationofResistivityData

Interpretationsectionswerecreatedforeachsurveylineusingresultsfromboththefieldresistivitydataandforwardmodels.Lines1through3wereinterpretedprimarilybasedonthefieldresistivitydata,whileforwardmodelswereusedasaguidelineforinterpretingthefielddata.Becauseofthemorecomplicatednatureofthefieldresistivitydatafromsurveylines4and5,interpretationswerebasedmoreheavilyontheforwardmodelsthanthefieldresistivitydata,yieldinga3layerinterpretationforline4anda2layerinterpretationforline5.BecauseofthelowersensitivityofthebottomoftheWennerSchlumbergerarray,theinterpretationsectiondoesnotaccuratelycharacterizethesurfaceoflayer3inanyofthelines.Becauseoftheremotenatureof2DDCresistivityandthechanceforvariabilityinthesubsurface,theinterpretationsarenonuniquesolutionstothefieldresistivitydata(Degnan,2001).Althoughitispossibletodevelopdifferentinterpretationsthatwouldalsobereasonablesolutionstothefield

resistivitydata,theadditionofinformationfromdriller'slogsandexcavationtrenchesmakesthefollowinginterpretedsectionslikelyscenarios.

Line1

Layer1consistsoftopsoilwithchertfragmentsoccurringatlandsurfaceandrangingdownto144to142meters(m)abovetheNorthAmericanVerticalDatumof1988(NAVD88).Clayisrepresentedaslayer2,butthethicknessofthislayercouldnotbedeterminedbecausenoconsistentthirdlayerwasfoundtodefinethelowerboundary.Layer3,limestone,ishorizontallydiscontinuous.Thecontactbetweenlayers2and3occursintermittentlybetween141to142minelevationinthenorthwesternpartofthesectionanddoesnotappearinthesoutheasternpartofthesection.Threeanomalieswereinterpretedalongthesoutheasternedgeofthesectioninlayer1,extendingbelowthesurfacetoadepthof1to1.5m(fig.22).Thislocationcorrespondstoastronganomalyseenclearlyinboththemagneticsusceptibilityandverticalgradientat(50,39)(fig.2).

Line2

Layer1,topsoilwithchertfragments,occursatthelandsurfaceandrangesdownto144.5to142.5minelevation.Layer2representsclaywithaninterpretedthicknessbetween1.5and2.5m.Layer3,composedoflimestone,isdividedintothreesectionsthatarelocatedonthenorthwesternpartoftheline.Therearethreeanomaliesinlayer1towardsthesoutheasternedgeofthesectionatdepthsof0to1m(fig.23).Theeasternmostanomalycorrespondstothelocationofananomalyinthemagneticsusceptibilityandtotalapparentelectricalconductivityaswellastheverticalgradient,near(50,36)(fig.2).Theremainingtwoanomaliesintheinterpretationsectionarecontainedwithintheboundsofzone1(fig.3).

Line3

Layer1,topsoilwithchertfragments,occursintheupper1to1.5mofthesection.Thesurfaceoflayer2,clay,wasinterpretedtobebetween142.5melevationalongthesouthernedgeofthesectionand141melevationalongthenorthernedgeofthesectionandtorangeinthicknessfrom2to2.5m.Layer3representslimestoneextendingfromthebottomoflayer2tothebottomofthesection.Thesurfaceofthelimestonestartsatabout140minelevationtothesouthanddescendsdiscontinuouslytoabout139melevationatthelocationdistanceof27m.Nolowresistivityanomalieswerelocatedintheinvertedfieldresistivity(fig.24).

Line4

Theresistivitylinecrossedthroughsurfaceexposuresofsmallarmswasteandbarbedwirealongtheentirelengthoftheline,whichmayhavecreatedapathforcurrentflowgeneratinglarge,lowresistivityanomaliesatgreaterdepthsthanmayberealistic.However,theforwardmodelwouldbeunabletopredictthisresponsecausedbythesurfacedebris,andthereforealsoreflectsthedeepanomaliesthatmaybeanartifactofsurficialdebris.

Topsoilandchertfragments(layer1)wereinterpretedtobeasthinas0.5mnearthesouthernedgeofthesectionandasthickas2.5malongthenorthernedgeofthesection.Alayerofchertgravelandcobble,rangingfromlessthan0.25mtoabout1.0metersthick,isinterpretedtocutcontinuouslythroughlayer1.Layer2(clay)rangesinelevationfromabout131malongthesouthernedgeofthesectiontoabout129matthenorthernedgeofthesection.Limestone(layer3)rangesinelevationfromabout128.5malongthesouthernedgeofthesectiontoabout129.5matlocationdistance15mthendecreasesinelevationtoabout129matthesouthernedgeofthesection(fig.25).Seveninterpretedlowresistivityanomaliesofvaryinglengthoccurredwithinlayers1and2,possiblyresultingfromthebarbedwirefoundnearthesurface.

Line5

Layer1,composedoftopsoilwithchertfragments,isfoundfromanelevationofabout130mtolandsurface.Thesecondlayer,interpretedtobeclay,extendsbelowthebottomofthesectiontoanunknowndepth.Severallowresistivityanomalieswerelocatedinlayer1oftheinvertedfieldresistivitydata.Theseanomaliesweremodeledinlayer1(topsoilwithchertfragments)oftheforwardmodelforsurveyline5.Forwardmodelingresultswereusedtoapproximatethedepthandsizeoftheseanomalies(fig.26).Theinterpretationsectionofresistivitydatafromline5showsascatteringoflowresistivityanomaliesintheeasternpartofthesectiontoadepthofabout1.5mbelowthesurface.ThetimedomainIPdatasupportsthisdepthanddistribution.Itislikelythatthesurficialwasteextendsintothesubsurfaceabout1.5minzone3(fig.8)atthislocation.

Figure22.Sectionshowinginterpretationofinvertedfieldresistivity,invertedmodelresistivity,andforwardmodelsectionsfromsurveyline1,AOC3.


ExcavationofSelectedAnomaliestoAssessAccuracyofGeophysicalSurveys

ExcavationwasperformedatAOCs3and7toexploreselectedanomaliesandsuspicioussurfacedebrisandtoassesstheaccuracyofthegeophysicalsurveys.Atotalofninelocationswereexcavatedduringtwoevents(trips)inAOCs3(E1,E2,E3fig.3)and7(E4throughE8fig.8).Excavatedsoilwassegregatedbydepthandplacedonatarp.WastecharacterizationwasperformedtwicebytheUSACE,whichconsistedoffillingabucketwithexcavatedsoilandthendeterminingtheweightandvolumeofsoilandsmallarmswaste.Atractormountedbackhoewasusedtoexcavatetheselectedareas.

AOC3

Trench1(E1),orientedapproximatelyeasttowest,(fig.3)wascompletedtoadepthof0.6matAOC3neartheeastbankoftheephemeralstream.Thislocationwaschosenbecauseofthescatteringofsmallarmswastevisibleinthesubstrateofthestreamchannel.Smallarmswastewasfoundscatteredthroughoutabrownsiltyclaysoilmatrixwithchertfragmentstoadepthofapproximately0.3m.Asoilsamplewascollectedatadepthofapproximately0.1to0.15m,inthesamezoneasthesmallarmswaste.Thesamplecontainedapproximately1volumetricpercentsmallarmswaste.Noanomalieswerefoundinthislocationbyanygeophysicalmethodusedinthisstudy,mostlikelybecauseofthenoncontinuousscatteringofasmallquantityofmetallicwaste.

Thesecond(E2)andthird(E3)trencheswerepositionedtofurtherinvestigatethesouthernmostanomalyfoundinzone1intheEMandmagneticresultsnear(50,42)(fig.2),aswellasinsurveyline1ofthe2DDCresistivityandtimedomainsurveys(fig.12).E2(fig.3)wasexcavatedtoabout1mbelowlandsurface.Nometallicdebriswasfoundatthislocation.AfterreexaminationofthefielddatafromtheEMandmagneticsurveys,excavationwasrepositionedtoE3.DuringexcavationofE3,aflattened55gallondrumwasremovedfromapproximately0.3mbelowlandsurface(fig.27A).Thisdrumwasmostlikelythecauseoftheanomalyseeninfigure2.

AOC7

FivetrencheswerecompletedatAOC7.Thefirsttrench,E4(fig.8),wasapproximately0.8mdeepandopenedgenerallyinawesttoeastdirectionbeginninginthestreambednearthesouthwestcornerofAOC7neargridlocation(35,12).Ametalpostwasremovedfromthealluvium,whichconsistedofsiltandchertfragments.Althoughverticalgradientdatashowedananomalyatthislocation,theEMdatadidnotshowasimilarfeature.Thisdiscrepancywaslikelycausedbythepowerline'sinfluenceovertheGEM2withinthepowerlinecorridor,whilethemagnetometerwasstillabletosuccessfullylocatemetallicdebris.

Thesecondtrench,E5(fig.8),wasopenedneargridlocation(50,81)intheeastbankofTysonHollowCreekinanorthtosouthdirectionandextendedtoadepthofapproximately0.3m.Thissitewaschosenbecauseofascatteringofsmallarmswasteonthesurfaceandbecausegrasshadfailedtogrowatthislocationalthoughthemajorityofthesitewasheavilyvegetated.TheEMandmagnetictechniquesdidnotshowanyanomaliesinthislocation.Thesoilconsistedofsiltyclaywithchertfragments,andsmallarmswasteappearedtoextendtoadepthofapproximately0.08to0.10m.Althoughsmallarmswastewasfoundatthesurface,therewasnoindicationthatthisdepositextendedintothesubsurfaceinhighconcentrations.Therefore,itisreasonablethatnoanomalieswerefoundusingthesespecificgeophysicalmethods.

E6,E7,andE8werethethird,fourth,andfifthtrenches(fig.8)andwereeastofthestreambankwheresmallarmswastewasexposedatthesurface(fig.7B)andEM,magnetic,2DDCresistivity,andtimedomainIPdataexhibitedanomalies(figs.6and15).E6wasopenedneargridlocation(55,51),generallyinawesttoeastdirectiontoadepthofapproximately0.9m.Smallarmswasteappearedtoextendtoadepthofapproximately0.4to0.5m.E7wasexcavatedneargridlocation(55,69),generallyinanorthtosouthdirectiontoadepthofapproximately0.6m.Smallarmswastewascontainedwithinthefirst0.1m.BarbedwirewaslocatedinthevicinityofE6andE7(fig.7B).E8wasexcavatedneargridlocation(55,54)toadepthofalmost1m.Smallarmswaste(fig.27B)wasfoundwithintheupper0.5minthistrench.

Figure27A1.PhotographstakenduringexcavationactivitiesatA,AOC3,showingtheremainsofa55gallondruminE3,andB,AOC7,showingsmallarmswastefoundinE8.(May2004).

Figure27A2.PhotographstakenduringexcavationactivitiesatA,AOC3,showingtheremainsofa55gallondruminE3,andB,AOC7,showingsmallarmswastefoundinE8.(May2004).

Figure27.PhotographstakenduringexcavationactivitiesatA,AOC3,showingtheremainsofa55gallondruminE3,andB,AOC7,showingsmallarmswastefoundinE8.(May2004).

SummaryandConclusionsTheformerTysonValleyPowderFarmnearEureka,Missouri,wasusedprimarilyasastoragefacilityfortheproductionofsmallarmsammunitionatthenearbySt.LouisOrdnancePlantduring194147and195161,althoughmunitionstestinganddisposaltookplaceonsiteaswell.DuringU.S.Armyactivityatthesite,shellcasings,munitions,munitionscomponents,storagedrums,andmiscellaneousmetallicmaterialsweredisposedofthroughouttheproperty,remnantsofwhichcanstillbeseenonthesurfaceandarebelievedtocontinueintothesubsurface.However,littlehistoricalinformationexistsdescribingdisposalpractices.Threeareasofconcern(AOC3,AOC7,andAOC10),previouslyidentifiedbytheU.S.ArmyCorpsofEngineers,wereselectedinspring2004forinvestigationbytheU.S.GeologicalSurvey,incooperationwiththeU.S.ArmyCorpsofEngineers,usingfoursurfacegeophysicalmethods.

Electromagneticandmagneticmethodswereusedtodeterminethesubsurfacearealextentofmetallicanomalies.Resultsfromthesemethodswereusedtocreatemapsidentifyingzonesofanomalieswithineachoftheareasofconcern.Severalzoneswerethenselectedforfurtherinvestigationusingtwodimensionaldirectcurrentresistivityandtimedomaininducedpolarization(IP)methodstocharacterizetheverticalextentoftheanomaliesintheselectedzones.Usinganinversionprocess,sectionsofthesubsurfaceweredevelopedfromthedataandwerecomparedtoanomalylocationsfromtheelectromagneticandmagneticsurveys.Excavationsweremadeatselectedlocationstochecktheresultsofthefourgeophysicalmethods.ThegeophysicalmethodsselectedforuseinthisstudywereusefulindeterminingthearealandverticalextentofmetallicwastewithintheformerTysonValleyPowderFarm.However,electromagneticandmagneticmethodswerenotabletodifferentiatemagneticscrapmetalfromnonmagneticmetallicsmallarmswaste,mostlikelybecauseofthesmallsizeandscattereddistributionofthesmallarmswaste,inadditiontothemixingofbothtypesofdebriswithinthesubsurface.

Electromagneticandmagneticdatashowedascatteringofanomaliesinallthreeareasofconcern.Anomalouszoneswereidentifiedandmappedzones12inAOC3,zones37inAOC7,andzones812inAOC10.Zones1,3,and5wereselectedforfurtherinvestigationconcerningtheverticalextentoftheanomalies.

Inzone1(AOC3),sectionsdevelopedfromtheresistivitydataalongsurveylines1and2indicatedthepresenceofanomaliesinlayer1(topsoilwithchertfragments).SectionsfromthetimedomainIPmeasurementsforsurveylines1,2,and3showedagreateroccurrenceofanomaliesinlayer1andextendingintolayer2.Thelackoflowresistivityanomaliesshownintheresistivitysectioncouldpossiblybeexplainedbythehighconcentrationofhighlyresistivechertfragmentsinlayer1.Thechertcouldhavebeenactingasaninsulator,maskingthelessresistiveinclusionsofsmallarmswaste.However,oncethesmallarmswastewas"charged"usingthetimedomainIPmethod,itshowedagreaterresponsecomparedtothesurroundingtopsoilandchertfragments.Excavationsshowedburiedscrapmetalandscatteredsmallarmswasteinzone1,anddidnotindicatethepresenceofanyhighdensitycontinuoussmallarmswastedeposits.Basedonalloftheresults,anomaliesinAOC3werebelievedtobeascatteringofavarietyofmetallicwastethatextendsfromthesurfacetoadepthofapproximately1meter,possiblyasdeepas1.5meters.

Inzone3(AOC7),resistivityline5crossedzone3throughsurfacedebrisincluding1inchdiametermetalcableandsheetmetal.Thefieldresistivitysectionforline5showedascatteringoflowresistivityanomaliesintheeasternpartofthesectiontoadepthofapproximately1.5metersbelowthesurface.ThetimedomainIPsectionconfirmedthisdepthanddistribution.Visualreconnaissanceshowedthemetalcableenteringthegroundinmultiplelocations.Thescatteredsurfacemetallikelyextendsintothegroundtoadepthofapproximately1.5meters,possiblyto2meters,belowthesurface.

Zone5(AOC7)wasbisectedlengthwisebyresistivityline4andcrossedthroughmultiplesurfaceexposuresofshellcasingsandbarbedwire.Theresistivitysectionshowedanomaliesextendingtoamaximumof1.5metersbelowthesurface.Excavationsalongtheresistivitylineshowedsmallarmswastepresentinthesoiltoanapproximatedepthof0.5meterbelowthelandsurface,althoughtheinterpretationofresistivitydataindicatesanomaliesextendtoagreaterdepth.Barbedwirealongthesurveylinemayhavecreatedapathforcurrentflow,causinglowresistivityanomaliestoextendbelowtheiractualdepths.

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Appendix1.GeoreferencedlocationswithinAOC3(table11),AOC7(table12),andAOC10(table13).


[AllunitsareinmetersCoordinateSystem:UniversalTransverseMercaterZone15,NorthAmericanDatumof1983,elevationisinmetersabovetheNorthAmericanVerticalDatumof1988N/A,notapplicable]

LineLocation MarkLocation Northing Easting Elevation PointDescription3 0 4268411.411 713528.494 148.4161 Gridpoint3 50 4268390.604 713572.594 143.2731 Gridpoint6 0 4268408.512 713528.3998 148.4859 Gridpoint6 50 4268387.45 713572.3893 143.4366 Gridpoint9 0 4268405.665 713528.0822 148.8196 Gridpoint 9 50 4268384.548 713572.0385 143.5966 Gridpoint9 50 4268384.371 713572.008 143.6951 Gridpoint12 0 4268402.793 713527.7922 149.0879 Gridpoint12 45 4268383.553 713566.8536 143.343 Gridpoint12 50 4268381.361 713571.5122 143.7705 Gridpoint 15 0 4268399.895 713527.6211 149.4011 Gridpoint15 45 4268380.56 713566.238 145.263 Gridpoint15 50 4268378.161 713570.9369 143.9991 Gridpoint18 0 4268397.395 713527.5124 149.9289 Gridpoint18 45 4268377.685 713566.0703 143.8356 Gridpoint 18 45 4268377.665 713566.0809 143.8836 Gridpoint18 50 4268374.814 713570.7857 144.2181 Gridpoint21 0 4268395.016 713527.1923 150.2409 Gridpoint21 45 4268374.495 713565.5861 144.011 Gridpoint21 50 4268372.08 713570.0079 144.2701 Gridpoint 24 0 4268391.641 713526.7689 150.3229 Gridpoint24 50 4268369.602 713569.6751 144.3631 Gridpoint27 0 4268388.601 713526.5006 150.3344 Gridpoint27 50 4268365.958 713569.3766 144.6166 Gridpoint30 0 4268385.615 713526.1987 150.2949 Gridpoint30 50 4268363.21 713569.1842 144.8636 Gridpoint33 0 4268382.923 713525.9751 150.3119 Gridpoint33 50 4268360.027 713568.8431 144.9671 Gridpoint36 0 4268379.637 713525.6574 150.3314 Gridpoint

36 50 4268358.04 713567.8629 145.0996 Gridpoint 39 0 4268376.6 713525.3768 150.3339 Gridpoint42 0 4268373.677 713524.9511 150.1584 Gridpoint45 0 4268370.824 713524.8305 150.2249 Gridpoint48 0 4268367.634 713524.561 150.4749 GridpointN/A N/A 4268401.216 713570.7704 142.8616 MonitoringWell:MW3 N/A N/A 4268395.697 713521.4441 150.6224 NorthwestcornerofthePoppingKettlebuildingN/A N/A 4268395.16 713570.5174 143.0901 Yellowbenchmarkdisk:RANDAPLS2579



MarkLocation LineLocation Northing Easting Elevation PointDescription0 0 4267928.137 712809.2012 135.95 Gridpoint0 25 4267929.988 712784.4486 134.38 Gridpoint0 25 4267929.965 712784.764 134.36 Gridpoint3 0 4267932.789 712808.7444 133.88 Gridpoint3 25 4267932.849 712784.8756 134.42 Gridpoint 6 0 4267935.804 712809.295 133.71 Gridpoint6 25 4267935.908 712785.3969 134.52 Gridpoint9 0 4267936.653 712810.5884 135.29 Gridpoint9 0 4268061.566 712803.2501 134.42 Gridpoint9 25 4267938.81 712785.8075 134.42 Gridpoint 12 0 4267939.601 712811.0294 134.99 Gridpoint12 30 4267942.002 712781.357 133.46 Gridpoint15 0 4267942.792 712811.4596 135.11 Gridpoint15 30 4267945.147 712781.7472 133.30 Gridpoint18 0 4267945.728 712811.8017 134.90 Gridpoint 18 30 4267948.131 712782.1512 133.16 Gridpoint21 0 4267948.657 712812.2523 134.66 Gridpoint21 30 4267950.94 712782.6141 133.05 Gridpoint24 0 4267951.648 712812.7039 134.43 Gridpoint24 30 4267954.042 712783.0265 133.01 Gridpoint 27 0 4267954.658 712813.0066 134.38 Gridpoint27 35 4267957.195 712778.4306 132.48 Gridpoint30 0 4267957.627 712813.4741 134.37 Gridpoint30 35 4267960.497 712778.7926 132.45 Gridpoint33 0 4267960.612 712813.8225 134.43 Gridpoint33 35 4267963.107 712779.0301 132.32 Gridpoint36 0 4267963.598 712814.2095 134.38 Gridpoint36 40 4267966.208 712774.7161 132.35 Gridpoint39 0 4267966.37 712814.5616 134.34 Gridpoint39 40 4267969.336 712774.8814 132.31 Gridpoint 42 0 4267969.572 712814.9288 134.29 Gridpoint42 40 4267972.52 712775.316 132.13 Gridpoint45 0 4267972.965 712815.3445 134.83 Gridpoint45 40 4267975.205 712775.7193 132.17 Gridpoint48 40 4267978.272 712776.4123 132.53 Gridpoint 51 40 4267980.428 712776.7662 132.67 Gridpoint54 0 4267980.992 712816.8908 135.00 Gridpoint54 45 4267983.524 712772.6194 132.67 Gridpoint57 45 4267986.666 712772.9462 132.54 Gridpoint

60 45 4267990.015 712773.4244 132.29 Gridpoint 63 45 4267992.336 712773.8831 132.02 Gridpoint66 45 4267995.254 712774.3551 131.80 Gridpoint69 45 4267998.001 712774.6861 131.58 Gridpoint72 45 4268001.03 712775.3072 131.86 Gridpoint111 0 4268037.658 712824.3585 134.96 Gridpoint 114 0 4268040.628 712824.7071 134.83 Gridpoint114 0 4268040.892 712824.746 134.86 Gridpoint114 5 4268040.956 712819.9719 134.79 Gridpoint117 0 4268043.589 712825.2137 134.76 Gridpoint117 5 4268043.628 712820.2921 134.76 Gridpoint 120 0 4268046.475 712825.5124 134.75 Gridpoint120 5 4268046.532 712820.7092 134.93 Gridpoint123 0 4268049.451 712826.0076 134.75 Gridpoint123 5 4268049.645 712821.0606 134.80 Gridpoint123 40 4268050.684 712786.2554 132.70 GridpointN/A N/A 4267890.814 712786.2602 135.07 Powerpole:PP364779N/A N/A 4267923.064 712829.4296 136.50 Powerpole:PP364780N/A N/A 4267942.26 712782.726 133.49 Powerpole:PP364790



LineLocation MarkLocation Northing Easting Elevation PointDescription0 0 4268052.919 712801.9002 134.54 Gridpoint0 15 4268053.402 712787.1048 133.65 Gridpoint9 0 4268061.64 712803.2616 134.42 Gridpoint9 20 4268062.441 712783.741 132.53 Gridpoint27 0 4268079.493 712805.8849 134.15 Gridpoint 36 0 4268088.361 712807.1011 134.10 Gridpoint42 0 4268094.338 712807.6285 133.90 Gridpoint45 0 4268097.325 712807.942 133.73 Gridpoint48 0 4268100.268 712808.3141 133.67 Gridpoint51 0 4268103.282 712808.6508 133.61 Gridpoint 54 0 4268106.277 712809.0405 133.70 Gridpoint54 5 4268106.699 712804.142 133.64 Gridpoint57 0 4268109.198 712809.3741 133.73 Gridpoint57 5 4268109.636 712804.4055 133.74 Gridpoint60 0 4268112.174 712809.7435 133.65 Gridpoint 60 5 4268112.489 712804.8566 133.70 Gridpoint63 0 4268115.12 712810.134 133.65 Gridpoint63 10 4268115.486 712800.2782 133.70 Gridpoint66 0 4268118.116 712810.4866 133.64 Gridpoint66 15 4268118.839 712795.6781 133.69 Gridpoint 69 0 4268121.182 712810.9077 133.54 Gridpoint69 15 4268121.83 712796.1919 133.61 Gridpoint72 0 4268124.062 712811.3565 133.51 Gridpoint72 15 4268124.829 712796.5147 133.43 Gridpoint75 0 4268127.052 712811.7302 133.45 Gridpoint 75 15 4268127.731 712796.8367 133.36 Gridpoint78 0 4268130.043 712812.2016 133.47 Gridpoint78 20 4268130.996 712792.4007 133.36 Gridpoint

81 0 4268132.94 712812.5533 133.49 Gridpoint81 0 4268132.976 712812.6697 133.47 Gridpoint 81 25 4268134.265 712787.7501 133.48 Gridpoint84 0 4268135.926 712812.9699 133.53 Gridpoint84 25 4268137.166 712788.1385 133.45 Gridpoint87 0 4268138.955 712813.4883 133.57 Gridpoint87 25 4268140.127 712788.6337 133.39 Gridpoint90 25 4268143.117 712788.9688 133.39 Gridpoint93 25 4268146.107 712789.3261 133.41 Gridpoint96 30 4268149.417 712784.7857 133.33 Gridpoint99 35 4268152.599 712780.102 133.27 Gridpoint102 35 4268155.528 712780.4485 133.30 Gridpoint 105 35 4268159.628 712780.9841 133.32 Gridpoint108 35 4268162.788 712781.5416 133.39 Gridpoint111 25 4268164.785 712791.7136 133.16 Gridpoint111 35 4268165.39 712781.7606 133.38 Gridpoint114 30 4268168.19 712787.1629 133.28 Gridpoint 114 40 4268169.024 712777.2493 133.08 Gridpoint

Appendix21.GraphsrepresentingthetotalpercentfrequencyofoccurrenceforspecificdatavaluesatAOC3forA,totalapparentelectricalconductivityB,magneticsusceptibilityat2,070HzandC,verticalgradient.

Appendix22.GraphsrepresentingthetotalpercentfrequencyofoccurrenceforspecificdatavaluesatAOC7forA,magneticsusceptibilityat2,070HzandB,verticalgradient.

Appendix23.GraphsrepresentingthetotalpercentfrequencyofoccurrenceforspecificdatavaluesatAOC10forA,magneticsusceptibilityat2070HzandB,verticalgradient.

Appendix3.EnvironmentalnoisetestsonA,April21,2004andB,April22,2004.Theyaxisrepresentstheamplitudeofthereceivedsignalthexaxisrepresentsthespecificfrequenciesatwhichthesignaloccurred.Singlespikesat2,030Hz5,010Hz9,030Hz13,830Hzand20,010HzaretheresultoftheprogrammedtransmissionfrequenciesoftheGEM2andarenotassociatedwithenvironmentalnoise.

Appendix4.Tableshowingcoordinatesofzoneboundaries.[AllunitsareinmetersCoordinateSystem:UniversalTransverseMercatorZone15,NorthAmericanDatumof1983]

Zone Easting Northing1 713562 42683501 713572 42683501 713574 42683601 713566 42684001 713553 4268400 2 713528 42683802 713535 42683902 713536 42683802 713529 4268390

3 712817 42680003 712806 42680003 712799 42680203 712787 42680303 712783 42680503 712791 42680503 712812 42680403 712822 4268020 4 712824 42680404 712818 42680404 712818 42680504 712825 4268050 5 712766 42679805 712760 42679805 712769 42680205 712771 42680005 712761 4268000 6 712796 42679606 712800 42679606 712795 42679606 712792 42679607 712808 42679707 712805 42679807 712796 42679907 712797 42680007 712807 42680007 712817 42679907 712815 4267970 8 712730 42681408 712728 42681508 712746 42681708 712760 42681508 712747 4268130 9 712796 42680609 712805 42680809 712803 42681009 712786 42681209 712776 42681009 712780 4268080 10 712798 426812010 712803 426813010 712799 426813010 712792 4268130 11 712812 426815011 712814 426816011 712811 426815011 712815 4268150 12 712791 426816012 712776 426816012 712778 426817012 712792 4268170

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surface geophysical investigation of the areal and vertical extent of metallic waste at the former...

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