T.OwenK.Park

DredgingDredging

DredgingmethodsDredgingmethodsCasestudyCasestudyMethodsformitigatingadverseeffectsMethodsformitigatingadverseeffectsCommentsandconclusionsCommentsandconclusions

Dredging istheprocessofunderwaterremovalofmaterialfromthebedorbanksofawaterwayanddisposingthematerialatadifferentlocation.

Classification Purposes ofdredgingaretodeepen/widenwaterwaysfornavigation,toregaincapacitywithinreservoirs,ortoreplenishsandonbeaches.

Locations fordredgingincluderivers,reservoirs,andseashores.

DefinitionofdredgingDefinitionofdredging

LawsandRegulations,andAgenciesLawsandRegulations,andAgenciesU.S.LawsandRegulations,andAgenciesMajorEnvironmentalLawsandRegulations

NationalEnvironmentalPolicyActof1969 ComprehensiveEnvironmentalResponse,

CompensationandLiabilityActof1980 CleanAirAct ResourceConservationandRecoveryActof1976 FederalWaterPollutionControlActof1972

(amendedandrenamedtheCleanWaterActof1977)

RiversandHarborsActof1899(TheRefuseAct) MarineProtection,Research,andSanctuariesAct

of1972(commonlycalledtheOceanDumpingAct)

CoastalZoneManagementActof1972 EndangeredSpeciesActof1973 FishandWildlifeCoordinationActsof1934,

1956,and1958 ToxicSubstancesControlAct andmanymore(completelistcanbefoundat

USACEwebsite)Governancetoproceeddredgingproject (i.e.potentialpermittingagencies)

USNationalMarineFisheriesService USFishandWildlifeService USEnvironmentalProtectionAgency StateFishandGameAgencies StateWaterQualityCertifyingAgencies StateCoastalZoneManagementAgencies OtherFederalandStateAgencies

S.KoreanLawsandRegulations,andAgenciesMajorEnvironmentalLawsandRegulations

FundamentallawofEnvironmentalimpactassessment1990

LawofEnvironmentalimpactassessment1993

LawofEnvironmentalimpactassessmentinEnvironmental,Transportation,Disaster1999

LawofNaturalEnvironmentConservation1999

LawofAggregateCollection1991 LawofStream1961 Lawofwastemanagement2007

Governancetoproceeddredgingproject (Nationalriver)

MinistryofTransportationandMaritimeAffairs

MinistryofEnvironment (Localriverandstream)

Localgovernment LocalbranchofMOCTandME

PlanninganewdredgingprojectPlanninganewdredgingproject Designdredgingplanperoneofthefollowingmanuals

U.S.ArmyCorpsofEngineersEM111025025,DredgingandDredgedMaterialPlacementEngineeringManual

IntegratedNationalRiverRestorationManual2011,Korea

ConsiderationsforDredgingandDredgedMaterialDisposal Selectionofproperdredgeplantforagivenproject Selectionofproperequipment Determiningwhetherornottherewillbedredgingofcontaminatedmaterial(i.e.completing

apreprojectEnvironmentalAssessment) Adequatedisposalfacilities Longtermplanningformaintenancedredgingprojects Characterizationofsedimentstobedredgedtosupportanengineeringdesignofconfined

disposalareas Determiningthelevelsofsuspendedsolidsfromdisposalareasanddredgeoperations Disposalofcontaminatedsediments Controlofdredgingoperationtoensureenvironmentalprotection Determiningquantityofmaterialtobedredgedanddisposed Obtainingappropriatepermits Consultingwithlocalresident Determiningtheaffectsonriverresponse(i.e.headcutting,morphology,etc) Cost,Time

Dredging,perspectivefromriverDredging,perspectivefromrivermechanicsmechanics

Considerationofthemajorfactorscausingriverbedaggradation

DredgingaffectsonRivermorphologyintheupstreamanddownstreamdirection Longtemmodelingforassessingdredgingeffectshavetobecarriedoutbeforeprojectimplementation

Dredgingandstructuralmeasures,suchashydraulicstructurestostabilizeriverchannel,canbeconsideredforminimizingpostprojectmaintenance(e.g.)InMississippiRiver Bendwayweirscouldmakedredging

reducedby80%(RiverMechanicsp270)

ClassificationofDredgingMethodsClassificationofDredgingMethods

MechanicalDredges Liftthedredgedmaterialbymeansofdiggersorbuckets Excavatedmaterialisdumpedintodisposalbargesforunloadingatthedisposalsite Typicallynotselfpropelledandmustbetowedtotheworksite Typesincludedipperdredge,bucketdredge(withclamshell,orangepeel,ordraglinebucket),Grab,BedLeveler,Krabbelaar,

Snagboat,Amphibious Considerablefinematerialislostfrombucket,andthemaximumconcentrationofthesuspendedturbidityplumeistypicallyless

than1,000ppm.

HydraulicDredges Pickupthedredgedmaterialbymeansofsuctionpipesandpumps Excavatedmaterialisdisposedbymeansofahopper,pipelineor sidecasting Typicallyselfpropelled Typesincludesuctiondredges(Hopper,Dustpan,Cutterheadwithclosednosebasketorwithopennosebasket,Trailing,Auger,

Jetlift,Airlift),WaterInjection,Pneumatic, Cutterheaddredgesarethemostefficient,versatile,andwidelyused.

DustpanDredge

CutterheadDredge

BucketDredge

(1)HydraulicSuctionDredges(1)HydraulicSuctionDredges(advantages)LowcostandhighrateofproductionCanpumplongdistancewiththeaidofboosterpumpstations(disadvantages)Bulkingoffinesediment

sedimentdewateringrequired(properlocations)Hopperdredge:selfpropelled,shallowcoastalharborsDustpandredge:selfpropelled,fordredgingnoncohesivematerialCutterheaddredges:mostwidelyused,foralluvialmaterialincludingcompactedclaysandhardpans(Cost)US$3~6$/m3

cutterheadladderladderpumpcontrolshullmainpumpenginespud floatanddischargepipelinedisposalarea inletzonefinesedimentdepositsadjustableeffluentweir dischargeofclarifiedeffluent

(2)MechanicalDredges(2)MechanicalDredges Mechanical(bucket)dredges

Excavates submergedsedimentswithabucket Deliveraproducthavinglowwatercontent,buttheproductionrateislow

Disadvantages Finesedimentislostwhenraisedfromdeepunderwater Cangenerateconsiderableturbidity

Classification Dipperdredge Bucketdredge

Cost:US$3$10/m3

Dipperdredge

Bucketdredge

(3)Othermethods(3)Othermethods

Usedinreservoirsedimentdredging(casesinChina)Slurryforcedthroughthepipelinebythedifferentialheadbetweenthewatersurfaceinthereservoirandthedischargepoint (w/opump)Mobiletype,fixedtypeTwomajorlimitations lackofreliabilityofsystem limitedhydraulicgradient

useachamberwithinlets,outofwhichthewaterispumpedwiththeinletsclosed.Afterthat,excavationbegins

Casestudy(1)Casestudy(1) 4MajorRivers4MajorRiversRestorationProjRestorationProjectect

Projectforsecuringwatersupplyandmorefloodcontrolcapacitycopingwithclimatechange (1.3billionm3 forwatersupply,0.92m3forfloodcontrol)

Totaldredging:57millionm3

Floodwaterlevelwillbedecreased0.4m(YoungsanRiver)~3.9m(NakdongRiver)

Dredges:hydraulicdredgingships(deepchannel)+backhoe(shallowchannel)

Mitigationmeasuresforadverseeffects:Vacuumdredging+doublesiltprotectors+realtimeturbiditysensing

Casestudy(2)Casestudy(2) YantzeRiverYantzeRiver(20012010)6majorprojectsundertakenduringthecurrent10yearperiod(200110)Dredgingthe414kmstretchoftherivertoenablethepassageof1,000dwtbargefleetsEradicatingtheshoalsandrapidscreatedbytheconstructionoftheThreeGorgesDam(20112020)Dredgenext395kmareaandareasbelowtheThreeGorgeReservoirfor10,000dwtbargefleetsNext497kmstretchtoallow20,00050,000dwtbargesCompletethedredgeafter312kmreachinthenextreach(Budget)US0.2billiondollarsfor5yeardredgingproject

Casestudy(3)Casestudy(3) MissouriRiverMissouriRiver In1929,theMissouriRiverNavigation

Commissionestimatedthetotalamountofgoodsshippedontheriverannuallyat15milliontons(doesnotmeettheestimatebyuntil)

Forthenavigation,almostalloftheMissouriRiverwasdredgedfromthelower500 miles(800 km)oftheriver.

Alsothisriverhasbeencommerciallydredgedforatleast70years tosupplysandandgravelforconcreteandasphaltusedinconstructionandroadbuilding.(minimum:250,000tonsperyearin1935,maximum9milliontonsin2002)

EPAscorneddredginginMissouriRiver forinappropriateenvironmentalimpactassessmentrecently

Casestudy(4)Casestudy(4) LakeSpringfield,IllinoisLakeSpringfield,Illinois Builtin1934(1635haimpoundment,

73.9Mm3,4.5mdeep),butby1984,capacityreducedby13percent(storageloss:9.5Mm3)

primarypurposeistoserveasthesourceofdrinkingwaterandIllinoisrecreationcenter,aswellasthesourceofcondensercoolingwaterfortheutility'slakeshorepowerplant

(Reservoirdredging) during1987~1991,2.28Mm3dredged unitcost:US$3/m3 conventionalcutterheaddredgewasapplied fromthe2nd phase,boosterpumpwasused sediment:66%clay,33%silt,1%sand containmentdike1.2~7m,dewateredfor2yrs

effluentturbidity1~2mg/L

Casestudy(5)Casestudy(5) TheworldinDubai,UAETheworldinDubai,UAE Measuringapproximately9kminwidth

by7kminlength,thedevelopmentwillcoverapproximately9,340,000squaremeters

Byseabeddredging,over326millioncubicmetersofsand waspumpedtoformtheislandsaswellasbuildinga26kilometerlongovalshapebreakwater.

(procedures)1.UsinglargedredgesTSHD,withhopperswithaminimum

of18,000m3,reachingalevelof10meters.2.Sincetheheight10to7,theemptyingjobiscarriedoutby

smallerdredges3.Bytheuseofsmalldredgestheyusethemostamountof

materialthatcanbedepositedbyemptyingnormallyuntilthe5meters.

4.Toreachalevelof+3meters,theprojectionbyblastingthesand ismade.

MethodsformitigatingadverseMethodsformitigatingadverseeffectseffects

(1)Disposalofdredgedsediment(1)DisposalofdredgedsedimentBeneficialUsesofDredgedMaterialInclude:Aquaculture,ConstructionMaterial,Topsoil,BermCreation,Capping,LandCreation,ShoreProtection,BeachNourishment,FishandWildlifeHabitats,WetlandRestoration,FisheriesImprovement,andmore

Casestudy:PalosVerdesShelfPilotCappingProject,LowAngelesCounty,CA

PilotprojecttotesttheabilitytocapcontaminatedsedimentinplaceasapotentialcleanupactionforthePalosVerdesShelfSuperfundSite

Threecells werecappedwithvaryingcapthickness,sedimenttypes,andplacementmethods

ConstructionofthepilotcapcompletedSeptember2001,monitoringongoing

Casestudy:HillsboroughBayCDF,FL Beneficialusesincludedfishand

wildlifehabitats,andwetlandrestoration

Twocontaineddisposalfacilities(CDF)islandswerebuilt.Marsheswerecreatedalongshorelinesandnestinghabitatprovidedonislandsurfaces.Marshplantingandlimitedbioengineering(riprap)wasprovidedforphysicalprotection.Smoothcordgrasssprigs,withmangroveseedpodswereplantedinthemarshstand.

MethodsformitigatingadverseMethodsformitigatingadverseeffectseffects

(2)Alleviatewaterqualityperturbation(2)Alleviatewaterqualityperturbation Methodsofminimizingwaterqualityperturbation: UsingaSiltCurtain EffluentTreatment through

clarifiertanksandfiltrationunits Biofiltration infiltrationof

effluentthroughforestfloors(adverseeffectscouldoccurtotheforest,however,somethodnotwidelyused)

FishExclusionCurtain DredgingTimingWindows

avoidingdredginginlowflows,andduringfishmigration

WaterQualityMonitoring SpillContingencyPlan perthe

AESLEngineeringTechnicalReport

Methodsforminimizingadverseeffects: SiltCurtaintocontainturbidity Selectionofappropriatedredgingmethodto

minimizeresuspensionofsediments,andmaximizecaptureofcontaminatedsoil(i.e.usingacutterheadsuctiondredgewithclosednosebasket

ProperdisposalofcontaminatedsedimentinaproperlydesignedConfinedDisposalFacility(CDF)

MethodsformitigatingadverseMethodsformitigatingadverseeffectseffects

(3)minimizingriverchange(3)minimizingriverchange Adverseecologicaleffectsofdredginginclude,butarenotlimitedto:

Substrateremoval,andthushabitatandspeciesremoval,whichrequiresrecolonizationofdisturbedareas.

Alterationofbottomtopography,whichinturndestroyslocalhabitat. Localresuspensionofsedimentsandincreaseofturbidity. Spreadofsedimentandassociatedcontaminantsinthesurroundingsof

thedredgingsite. Disposalofcontaminatedsediment

TheConfinedDisposalFacilityatKetelmeerintheNetherlandsisagoodexampleofbestpractice.

MethodsformitigatingadverseeffectsMethodsformitigatingadverseeffects(3)minimizingriverchange(cont(3)minimizingriverchange(contd)d)

Rivermorphology Potentialeffectsofdredgingonrivermorphologyincludeheadcuttingand

bankcutting,resultinginlossofriversideproperty,andsteepeningoftheriversystem,includingtributaries.

CaseStudy:KawRiver,KansasCity,KS Cause:Sandandgravelminingfromriverbottomusingdredging

methods. Problem:Localizeddredgedareaswerereplenishedwithsand

erodedfromriverbanksandtributariesupstream,resultinginlossofriversideproperty,lossofriparianvegetation,degradationofbankstability,andlocalscouraroundbridgepiersandhydraulicstructures.

Solutions:Regulate wheresandandgraveldredgingisallowedsothatoverdredging(i.e.exhaustingtheriversystem)isavoided,andencouragesandandgravelpitminingoutsideoftheriversystem.

CommentsandConclusionsCommentsandConclusions ThetwomajorclassesofdredgersareHydraulicandMechanical. The

maintypesofdredgesincludesuction,bucket,anddipperdredges. Alotofdredgingprojectshavebeendoneandstillaregoingon inrivers,

reservoirsandseas. Advantagestodredgingincludeimprovingthedepthandwidthof

navigablewaterways,andusingdredgedmaterialforapplicationsincludingbermconstruction,wetlandsrestoration,beachreplenishment,andmuchmore.

Adverseeffectsincludedegradationofwaterquality,adverseenvironmentalimpacts,andadversegeomorphologicalimpacts,tonameafew.Tomitigatethenegativeimpacts,diversemethodsappropriatetoaparticularprojectshouldbeimplemented

Dredgingprojectsmustbeapprovedbymanyfederalandstategovernmentalagenciesandmustadheretoalonglistofregulations.

5.Conclusions5.Conclusions