1. 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)

2. 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)

3. 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.

4. Dredging = Underwater Excavation

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

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

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

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

9. Types of Dredges Mechanical Hydraulic Bucket Dipper Sidecast Hopper
Dustpan
Cutterhead

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

11. Dipper Dredges
Same Advantages and Limitations as for Bucket Dredges

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

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

14. 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

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

16. Cutterhead Dredge Operations

17. Pipeline Transport of Solids

18. Disposal Alternatives
Open-water Disposal
Confined Disposal
Habitat Development

19. Dewatering & Densification

20. 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

21. 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

22. 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

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

24. 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

25. 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

26. 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?)

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

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

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

30. 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

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