Dredging Engineering: Building & Maintaining Underwater Highways Bryan N. Jones, M.S., P.E. Coastal Engineer COLLINS ENGINEERS, INC. Civil, Structural,

Dredging Engineering:Building & Maintaining Underwater Highways

Bryan N. Jones, M.S., P.E.Coastal Engineer

COLLINS ENGINEERS, INC.Civil, Structural, Water Resources and Underwater Engineering

125-G Wappoo Creek Drive, Charleston, SC 29412

Phone:(843) 406-1300 E-mail: [email protected]

www.collinsengr.com

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Introduction

Historical Significance of Waterborne TransportationSafe and Efficient (95% of US trade through ports)Evolution of Ships (larger, wider, faster vessels)Evolution of Shipping (containerization)

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Navigation ChannelsFew rivers or harbors are naturally deep.Channel improvements for ships to enter/leave ports efficiently, quickly and safely.Designing, building, and maintaining channels compared to constructing underwater highways.First US projects in 1789, with congressional approval for lighthouse construction.

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Dredging = Underwater Excavation

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Early Forms of DredgingSpades & Buckets (Nile, Tigris, Euphrates)Agitation Dredging (Indus)Scraper Dredging (1435)Bag & Spoon (Netherlands)Revolving Chain “Mud Mill” (1500’s)

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Dredging ProjectsShort-Term Objective

Construct or maintain channels

Long-Term ObjectiveManagement and operation of disposal areas

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Project Design ConsiderationsLocation and quantitiesSediment properties and characteristicsEvaluate disposal alternativesIdentify social, environmental, and institutional factors

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Selection of Dredge Plant Equipment

Material CharacteristicsQuantitiesDredging DepthDistance to Disposal AreaContamination of SedimentsMethod of Disposal

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Types of Dredges

MechanicalBucketDipper

HydraulicSidecastHopperDustpanCutterhead

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Bucket DredgesAdvantages

Hard/Compact MaterialsPrecise control of excavation

LimitationsDifficult to retain finesLow production ratesRequires scow barges

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Dipper DredgesSame Advantages and Limitations as for Bucket Dredges

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Sidecaster DredgesAdvantages

Self-propelledRapid Response

LimitationsOpen water disposal onlySome material may return to the channel prism

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Dustpan Dredges

AdvantagesSelf-propelledHigh production ratesRapid deployment

LimitationsLoose materials onlyNo open water1000 ft pumping distance

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Hopper DredgesAdvantages

Work in open waterSelf-propelled vesselNo obstruction of trafficEconomical over long distances

LimitationsDeep draftNot continuousNo contaminated sedimentsNot effective around structures

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Cutterhead Pipeline Dredges

AdvantagesMost material typesContinuous operation

LimitationsNo open waterNot self-propelledPipeline is a navigation hazard

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Cutterhead Dredge Operations

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Pipeline Transport of Solids

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Disposal AlternativesOpen-water DisposalConfined Disposal Habitat Development

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Dewatering & Densification

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Long Term Dredge Material Management Plans

50-year typical project lifeDredged material characteristicsIdentification of placement sitesImplementation Plan (Party Responsibilities)Geotechnical ReportCost EstimatesHistoric/Archaeological ConcernsAgency Cooperation/CoordinationReal Estate and Local

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Environmental Challenges:Public Perception IS REALITY!

PastTerminology (spoil, sludge, disposal)Previous History

PresentPollution is a resource that is out of placeBeneficial Uses

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1969 – National Environmental Policy Act (NEPA)Environmental Impact AssessmentsBalance environmental/economic/social needs

1976 – Clean Water ActState & Federal Permitting

Marine Protection Research and Sanctuaries ActOcean placement of material

Endangered Species Act

Environmental Challenges:Legislation

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Time DelaysPermit FeesTesting for Contaminated Sediments Seasonal Restrictions

Environmental Challenges:Permit Requirements

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Beneficial Uses of Dredge Material :Pollution is merely a misplaced resource!

Habitat developmentWetlandsBird IslandsOyster Grounds

Beach nourishmentConstruction

Ports & HarborsHighways & Airports

AgricultureSolid Waste ManagementParks and recreation

MiamiBeach

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What is Involved with Dredging Projects?

EngineeringSurveys & DesignTidal HydraulicsPhysical Sediment Analysis

EnvironmentalLegal ComplianceAssess Needs and ImpactsChemical Analysis of Sediments

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Real EstateRights of EntryReleases from Liability

Local OrdinancesLand Use PlansZoningPublic Policy Issues

Economics (Who pays?)

What is Involved with Dredging Projects?

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Typical Dredging Contracts

Solicitation, Offer, and AwardContract ClausesSpecial Requirements/Restrictions

PermitsSchedules & ProgressShoaling/Additional Work

Plans & Specifications

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Dredging Contracts - SpecificationsGeneral RequirementsSpecial Requirements

PermitsSchedule & ProgressShoaling & Additional WorkFinal Examination & Acceptance

MeetingsQuality ControlEnvironmental Protection

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Site WorkDefinition of Payment ItemsCharacter of MaterialsPlacement of Dredge Material

Site Investigation – Material CharacteristicsLocal Regulations

Dredging Contracts - Specifications

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Measurement & PaymentPlace measure at dredge siteBin measure (Hopper Dredges)Place measure at placement site (very difficult!)Plant Rental/Lump SumPre- and Post-Dredging Hydrographic Surveys

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Dredging Contracts - Drawings“Specifications Govern” ClausePlan & Section Views of ChannelPlan & Section Views of Placement Site