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: bjones@collinsengr.com www.collinsengr.com

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

Navigation Channels Few 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.

Dredging = Underwater Excavation

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

Dredging Projects Short-Term Objective Long-Term Objective Construct or maintain channels Long-Term Objective Management and operation of disposal areas

Project Design Considerations Location and quantities Sediment properties and characteristics Evaluate disposal alternatives Identify social, environmental, and institutional factors

Selection of Dredge Plant Equipment Material Characteristics Quantities Dredging Depth Distance to Disposal Area Contamination of Sediments Method of Disposal

Types of Dredges Mechanical Hydraulic Bucket Dipper Sidecast Hopper Dustpan Cutterhead

Bucket Dredges Advantages Limitations Hard/Compact Materials Precise control of excavation Limitations Difficult to retain fines Low production rates Requires scow barges

Dipper Dredges Same Advantages and Limitations as for Bucket Dredges

Sidecaster Dredges Advantages Limitations Self-propelled Rapid Response Limitations Open water disposal only Some material may return to the channel prism

Dustpan Dredges Advantages Limitations Self-propelled High production rates Rapid deployment Limitations Loose materials only No open water 1000 ft pumping distance

Hopper Dredges Advantages Limitations Work in open water Self-propelled vessel No obstruction of traffic Economical over long distances Limitations Deep draft Not continuous No contaminated sediments Not effective around structures

Cutterhead Pipeline Dredges Advantages Most material types Continuous operation Limitations No open water Not self-propelled Pipeline is a navigation hazard

Cutterhead Dredge Operations

Pipeline Transport of Solids

Disposal Alternatives Open-water Disposal Confined Disposal Habitat Development

Dewatering & Densification

Long Term Dredge Material Management Plans 50-year typical project life Dredged material characteristics Identification of placement sites Implementation Plan (Party Responsibilities) Geotechnical Report Cost Estimates Historic/Archaeological Concerns Agency Cooperation/Coordination Real Estate and Local

Environmental Challenges: Public Perception IS REALITY! Past Terminology (spoil, sludge, disposal) Previous History Present Pollution is a resource that is out of place Beneficial Uses

Environmental Challenges: Legislation 1969 – National Environmental Policy Act (NEPA) Environmental Impact Assessments Balance environmental/economic/social needs 1976 – Clean Water Act State & Federal Permitting Marine Protection Research and Sanctuaries Act Ocean placement of material Endangered Species Act

Environmental Challenges: Permit Requirements Time Delays Permit Fees Testing for Contaminated Sediments Seasonal Restrictions

Beneficial Uses of Dredge Material : Pollution is merely a misplaced resource! Habitat development Wetlands Bird Islands Oyster Grounds Beach nourishment Construction Ports & Harbors Highways & Airports Agriculture Solid Waste Management Parks and recreation Miami Beach

What is Involved with Dredging Projects? Engineering Surveys & Design Tidal Hydraulics Physical Sediment Analysis Environmental Legal Compliance Assess Needs and Impacts Chemical Analysis of Sediments

What is Involved with Dredging Projects? Real Estate Rights of Entry Releases from Liability Local Ordinances Land Use Plans Zoning Public Policy Issues Economics (Who pays?)

Typical Dredging Contracts Solicitation, Offer, and Award Contract Clauses Special Requirements/Restrictions Permits Schedules & Progress Shoaling/Additional Work Plans & Specifications

Dredging Contracts - Specifications General Requirements Special Requirements Permits Schedule & Progress Shoaling & Additional Work Final Examination & Acceptance Meetings Quality Control Environmental Protection

Dredging Contracts - Specifications Site Work Definition of Payment Items Character of Materials Placement of Dredge Material Site Investigation – Material Characteristics Local Regulations

Measurement & Payment Place measure at dredge site Bin measure (Hopper Dredges) Place measure at placement site (very difficult!) Plant Rental/Lump Sum Pre- and Post-Dredging Hydrographic Surveys

Dredging Contracts - Drawings “Specifications Govern” Clause Plan & Section Views of Channel Plan & Section Views of Placement Site