Sediment Management Technologies
Sediment Management Technologies W. H. McAnally PhD, PE, D.CE, D.NE, F.ASCE Research Professor of Civil & Environmental Engineering Mississippi State University, USA. [email protected]
R. Kirby BSc, PhD, C.Geol, Dist.D.NE, FGS Director & Board Member Sediment Innovation Centre (SICEM) Emden, Germany. [email protected]
Port & Channel Sedimentation • Sediment accumulation reduces available depth • Dredging & disposal are expensive • Dredging & disposal are often environmentally disruptive • Environmental windows limit dredging • Placement sites are limited
Engineering Solutions Krone’s 3 ways to address sediment deposition: • Keep sediment out • Keep it moving • Remove it
Photos courtesy of Corps of Engineers
PIANC WG 102: Minimizing Harbor Siltation Six Methods Taxonomy METHOD 1. Keep Sediment Moving (KSM) and mainly passive:
DESCRIPTION Locate/relocate port to deeper water, locate berths alongside channels rather than on waterway margin, apply equilibrium regime theory concepts, dredge channels parallel to natural flow, etc. Longitudinal/perpendicular training walls/groins, dikes, or 2. KSM and passive sills. Bed -mounted, automatic pumps fed by water injection, and 3. KSM and active applicable at impounded or semi-enclosed basins; early stage (i.e. before consolidation) water injection alone; bar/shoal removal, scour/propeller jets, etc. 4. Keep Sediment Out For impounded docks, adopt low solids, surface water (KSO) and active intakes, or resort to intermediate settlement basins, etc. 5. KSO Through Passive For impounded docks, adopt low solids, surface water Structures: intakes, or resort to intermediate settlement basins, etc. 6. Keep Sediment Navigable Adopt Passive or Active Nautical Depth and Conditioning (KSN) and passive/active
COPRI: Sed Solutions Taxonomy CATEGORY
Prevention
STRATEGY
EXAMPLES
KSP – Keep Sediment in Place
Erosion control on land and/or bed and banks
KSO – Keep Sediment Out
Sediment Traps, Gates and Dikes, Channel Separations
KSM – Keep Sediment Moving
Training Structures, Agitation, Flocculation Reduction , Flows
KSN – Keep Sediment Navigable Treatment
Accommodation
DRS – Dredge and Remove Sediment
Nautical Depth Definition, Aerobic Agitation Placement in confined disposal facilities or offshore, Permanent beneficial uses
DPS – Dredge and Place Sediment
Bypass sediment (KSM), Temporary beneficial uses
Adapt (to Changing Sediment Regime)
Flexible infrastructure, opportunistic agriculture, coastal setbacks
Fine, Cohesive Sediments • • • • •
Diameter < 20 – 40 μm Form flocs – low density, mostly water Form Fluid Mud in high concentrations False acoustic “bottom” fathometer signals Require dredging large volumes of muddy water
Photos courtesy of Chris Zabawa, EPA
Nautical Depth
COUNTRY
PORT
The Netherlands
Rotterdam
Belgium
Zeebrugge
China
Yangtze
China
UK
Liang yungang Tianjing xingang Avonmouth
France
Dunkirk
France
Bordeaux
France Germany
Nantes - Saint Nazaire Emden
Thailand
Bangkok
Surinam
Paramaribo
China
Fluid Mud
Firm Bottom
French Guiana Cayenne
Fluid Mud in Sediment Profiles Sediment transport depth
Sediment concentration or density
Mixed layer mobile suspension
X
Secondary lutocline
X
Suspension
Stratified mobile suspension
(zero effective stress)
Primary lutocline Lutocline shear layer Zero velocity plane
X
Fluid mud Stationary fluid mud Deforming bed Stationary bed
Depth below water surface
Bed (measurable effective stress)
Fluid Mud
Passive Nautical Depth • Map Fluid Mud Density • Dredge to keep 1.2 kg/cu m below channel prism
Zeebrugge Harbor entrance density contours at project depth
Active Nautical Depth • Create and maintain fluid mud in channel/port by oxygenation & stirring • Presence of fluid mud prevents entry of new sediment • Vessels sail through muddy water • Example: Emden Port
Emden: Self-propelled hopper with low power underwater pump for infrequently fluidising, raising, oxidising and redepositing fluid mud. (Wurpts, 2005).
Emden Active Nautical Depth • Maintenance dredging reduced from 4X106 cu m/yr to 0 • Costs reduced from €12.5M to €2M/yr • Chemolithotrophic bacteria break down the Tri-butyl Tin • Formerly intractable problem has disappeared
Gulf Ports Project • PURPOSE: – Find feasible, affordable engineering solutions to reduce or eliminate port maintenance dredging requirements.
• APPROACH: – Identify sedimentation problems and causes – Devise approaches to decrease dredging costs.
Pascagoula • Two harbors • Deep draft port ~ 40+ ft • Both local and federal channels • Top 20 largest U.S. ports
• • • • •
Fluid mud Dredged every 18 months About $450,000 per cycle Limited disposal space Nautical depth would work
Conclusions • Sediment Management: – Can reduce dredging costs – Is sustainable – Comes in many different forms
• Nautical Depth is a proven solution – Used ~40 years in Rotterdam & worldwide – Should be used in U.S.
R. Kirby BSc, PhD, C.Geol, Dist.D.NE, FGS Director & Board Member Sediment Innovation Centre (SICEM) Emden, Germany. [email protected]
Port & Channel Sedimentation • Sediment accumulation reduces available depth • Dredging & disposal are expensive • Dredging & disposal are often environmentally disruptive • Environmental windows limit dredging • Placement sites are limited
Engineering Solutions Krone’s 3 ways to address sediment deposition: • Keep sediment out • Keep it moving • Remove it
Photos courtesy of Corps of Engineers
PIANC WG 102: Minimizing Harbor Siltation Six Methods Taxonomy METHOD 1. Keep Sediment Moving (KSM) and mainly passive:
DESCRIPTION Locate/relocate port to deeper water, locate berths alongside channels rather than on waterway margin, apply equilibrium regime theory concepts, dredge channels parallel to natural flow, etc. Longitudinal/perpendicular training walls/groins, dikes, or 2. KSM and passive sills. Bed -mounted, automatic pumps fed by water injection, and 3. KSM and active applicable at impounded or semi-enclosed basins; early stage (i.e. before consolidation) water injection alone; bar/shoal removal, scour/propeller jets, etc. 4. Keep Sediment Out For impounded docks, adopt low solids, surface water (KSO) and active intakes, or resort to intermediate settlement basins, etc. 5. KSO Through Passive For impounded docks, adopt low solids, surface water Structures: intakes, or resort to intermediate settlement basins, etc. 6. Keep Sediment Navigable Adopt Passive or Active Nautical Depth and Conditioning (KSN) and passive/active
COPRI: Sed Solutions Taxonomy CATEGORY
Prevention
STRATEGY
EXAMPLES
KSP – Keep Sediment in Place
Erosion control on land and/or bed and banks
KSO – Keep Sediment Out
Sediment Traps, Gates and Dikes, Channel Separations
KSM – Keep Sediment Moving
Training Structures, Agitation, Flocculation Reduction , Flows
KSN – Keep Sediment Navigable Treatment
Accommodation
DRS – Dredge and Remove Sediment
Nautical Depth Definition, Aerobic Agitation Placement in confined disposal facilities or offshore, Permanent beneficial uses
DPS – Dredge and Place Sediment
Bypass sediment (KSM), Temporary beneficial uses
Adapt (to Changing Sediment Regime)
Flexible infrastructure, opportunistic agriculture, coastal setbacks
Fine, Cohesive Sediments • • • • •
Diameter < 20 – 40 μm Form flocs – low density, mostly water Form Fluid Mud in high concentrations False acoustic “bottom” fathometer signals Require dredging large volumes of muddy water
Photos courtesy of Chris Zabawa, EPA
Nautical Depth
COUNTRY
PORT
The Netherlands
Rotterdam
Belgium
Zeebrugge
China
Yangtze
China
UK
Liang yungang Tianjing xingang Avonmouth
France
Dunkirk
France
Bordeaux
France Germany
Nantes - Saint Nazaire Emden
Thailand
Bangkok
Surinam
Paramaribo
China
Fluid Mud
Firm Bottom
French Guiana Cayenne
Fluid Mud in Sediment Profiles Sediment transport depth
Sediment concentration or density
Mixed layer mobile suspension
X
Secondary lutocline
X
Suspension
Stratified mobile suspension
(zero effective stress)
Primary lutocline Lutocline shear layer Zero velocity plane
X
Fluid mud Stationary fluid mud Deforming bed Stationary bed
Depth below water surface
Bed (measurable effective stress)
Fluid Mud
Passive Nautical Depth • Map Fluid Mud Density • Dredge to keep 1.2 kg/cu m below channel prism
Zeebrugge Harbor entrance density contours at project depth
Active Nautical Depth • Create and maintain fluid mud in channel/port by oxygenation & stirring • Presence of fluid mud prevents entry of new sediment • Vessels sail through muddy water • Example: Emden Port
Emden: Self-propelled hopper with low power underwater pump for infrequently fluidising, raising, oxidising and redepositing fluid mud. (Wurpts, 2005).
Emden Active Nautical Depth • Maintenance dredging reduced from 4X106 cu m/yr to 0 • Costs reduced from €12.5M to €2M/yr • Chemolithotrophic bacteria break down the Tri-butyl Tin • Formerly intractable problem has disappeared
Gulf Ports Project • PURPOSE: – Find feasible, affordable engineering solutions to reduce or eliminate port maintenance dredging requirements.
• APPROACH: – Identify sedimentation problems and causes – Devise approaches to decrease dredging costs.
Pascagoula • Two harbors • Deep draft port ~ 40+ ft • Both local and federal channels • Top 20 largest U.S. ports
• • • • •
Fluid mud Dredged every 18 months About $450,000 per cycle Limited disposal space Nautical depth would work
Conclusions • Sediment Management: – Can reduce dredging costs – Is sustainable – Comes in many different forms
• Nautical Depth is a proven solution – Used ~40 years in Rotterdam & worldwide – Should be used in U.S.
