dredging teo park 0419
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T.OwenK.Park
DredgingDredging
DredgingmethodsDredgingmethodsCasestudyCasestudyMethodsformitigatingadverseeffectsMethodsformitigatingadverseeffectsCommentsandconclusionsCommentsandconclusions
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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
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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)
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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
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(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
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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
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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
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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.
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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.
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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
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