Introduction to Sediment Remediation
Presented to:
Lower Passaic River Community Advisory Group
July 14, 2011
Overview
 Feasibility Considerations
• Conceptual Site Model
• Dredging / Capping
• Dredged Material Management
 Design
 Construction
The Practice of Contaminated Sediment
Management
Remediation
Risk, Inventory
Navigation
Restoration
Depth, Width
Habitat, Water
Quality
Some Important References
http://el.erdc.usace.army.mil/elpubs/pdf/trel08-4.pdf
http://www.epa.gov/superfund/health/conmedia/sediment/guidance.htm
Interpreting the Conceptual Site Model
 Areas of High
Concentration
 Areas of High
Inventory (Mass)
 Sediment Stability
Considerations
 Receptor
Pathways
A Simplified Look at the Sediment
ZONE
Water Column
SOME CONTAMINANT
TRANSPORT PROCESSES
Solids Transport
Bed Load Transport
Biologically Active Zone
Bioavailable Zone
Buried Contaminated Sediments
Native Geologic Materials
Erosion / Deposition,
Biological Uptake
Porewater flux,
Contaminant
degradation
Groundwater
discharge
SEDIMENT TRANSPORT
Sediment Stability
Some ways to assess sediment stability include:
Determine Bathymetric Changes
Evaluate Sediment Texture
Understand Geomorphology
Estimate Storm Event Velocities
Perform SedFlume or Gust Microcosm Experiments
Perform Sediment Transport Modeling
Some Key Topics for Remedy Selection
 Where to Remediate: Active vs. Monitored
Natural Recovery
 What method: Dredging vs. Capping (vs. Insitu)
 How to Manage the Sediments
 Effectiveness & Recontamination
 Other Site-Specific Factors
 NEEDS
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GOOD PREDICTIVE MODEL
COMMON SENSE
STAKEHOLDER INPUT
DREDGING
DREDGING:
Feasibility & Design
Considerations & Terminology
 Resuspension
 Residuals
 Dredged Material
Management
 Productivity
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Dredge Prism
Debris / Utilities / Structures
Dredging Technology
Delivery Techniques
Navigation
Slope Stability
Productivity
Contracting Approach
Dredging Advantages/Limitations
(per USEPA Guidance)
Advantages
Lower uncertainty for long-term
effectiveness*
More flexibility for future use
Less reliance on institutional
controls
Less time to achieve goals than
Monitored Natural Recovery
Allows for treatment/beneficial
use of sediments
* Where cleanup levels achieved
Limitations
More logistically complex and
costly
Treatment technologies still in
scale-up mode; may be costly
Disposal facilities / options may
be limited
Difficulty in estimating residual
contamination
Effects of resuspension and/or
volatilization
Temporary disruption of aquatic
community and habitat
Some Dredging Resuspension
Terminology (General Illustration)
Minimizing Sediment Resuspension
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Equipment Selection
Operator Experience
Best Management Practices (BMPs)
Containment (Curtains, Barriers, Sheetpile)
Innovative Approaches
Dredging Equipment Selection
Horizontal Profiler
CableArm
Horizontal Auger (MudCat)
Cutterhead
Source: Bean Environmental, Cable Arm
Some Best Management Practices for
Resuspension
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Monitoring
Bucket Closure Sensors
Lift Speed Control
Equilibration Time
Rinse Tank / Clean Bucket
Minimize Equipment Moves
Penetration Depth
Emerging Technologies for
Resuspension Control
 Control Zone
 Insitu Stabilization
RESUSPENSION
Resuspension Trends
FRACTION OF
MASS REMOVED
MASS
RATE
NORMAL OPERATING RANGE
DREDGE PRODUCTION
Navigation Sources of Resuspension
Photo provided by PANYNJ.
DREDGING RESIDUALS
Sampling of
Residuals
Dredge
Pre-dredging
Elevation
Of River Bottom
Design Cut Line
Contaminated Sediments
“Clean” Over-cut Sediments
Residual Sediments
Overdredge Depth
Residuals Tidbits
 Prediction: The concentration of contaminants in
dredging residuals is an integration of the
concentration of the last bucket dredged.
 Reynolds Metals Case Study: After each
dredging pass, approximately half of the dredge
certification units (cells) met the cleanup criteria.
One cell was dredged 13 times.
 Operator skill appears to be one of the keys to
reducing residuals.
 Backfill can be effective used to attenuate
residuals.
Managing Dredging Residuals
 Good Inventory Characterization & Dredge to
Defined Elevation with backfill
 Redredging
 Specialty Equipment
 Backfilling (Dilution)
 Capping
Dredged Material Management
Disposal
 CAD Cells
 CDFs
 Placement Sites
(Brownfields)
 Decontamination
 Waste Management
Facilities (Landfills)
Handling
 Delivery: Barge vs. Hydraulic
 Dewatering vs. Desiccation
 Water Treatment
 Transport: Barge vs. Rail vs.
Truck
Dredged Material Management Options
Decontamination Technologies
 Minergy
 Biogenesis
 Endesco / GTI (now Volcano)
 Upcycle
Source: http://www.state.nj.us/transportation/works/maritime
Bean Environmental Bonacavor
Hydraulic Excavator Dredge
Putting it All Together
Dredging
Scow Transport
Hydraulic Offloading
Courtesy of John Henningson; Henningson Environmental Services, Inc.
Dewatering
Stockpile for Treatment /
Disposal
Off-site Disposal or
Beneficial Use
http://www.dfo-mpo.gc.ca/regions/central/pub/fact-fait-mb/mb1_e.htm
http://www.foxrivercleanup.com/foxrivercleanup/photo+gallery/default.asp
http://www.foxrivercleanup.com/foxrivercleanup/photo+gallery/default.asp
Water Treatment Plant
CAPPING
Capping Feasibility & Design
Considerations & Terminology
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Cap Stability - Erosion
Cap Structure
Navigation
Porewater Fluxes
Flooding Impacts
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Thickness
Grain Size
Filter Design
Maintenance
Borrow Source Identification
Reactive Layers
Physical Barriers
Performance criteria
Pre-dredging
Habitat Layers
Capping Advantages/Limitations
(per USEPA Guidance)
Advantages
Quickly reduce exposures
Clean substrate for benthic re-colonization
May enhance habitat
Less infrastructure for material handling
Less potential for resuspension
Limitations
Contaminated sediment remains –
could be released if disturbed or
break through
Possibility of sediment disruption
during placement
Shallow water may require
inconvenient institutional controls
(e.g., boating restrictions)
Cap may alter hydrologic regime
Avoids risks associated with material
treatment or disposal
Cap materials may alter biological
community
Usually lower cost and less disruption
than dredging and sediment
treatment/disposal
Long-term monitoring and
maintenance
Placement Techniques
Conveyor
Hydraulic Diffuser
Split-Hull Barge
Clamshell
Cap Placement Equipment - Spreader
Source: Bean Environmental
Examples of Completed Capping
Projects (Year Completed)
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St. Paul Waterway, WA (1991)*
Marathon Battery, NY (1994)
Eagle Harbor, WA (2002)
Grasse River, NY (2005) – pilot study
Anacostia River, MD (2007) – pilot studies
Fox River, WI (ongoing)
*part of the Commencement Bay - Nearshore Tideflats Superfund Site
which consists of 8 contaminated sediment problem areas within 6
marine waterways.
Implementation / Construction Issues
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Processing Facility Siting
Contractor Selection
Operator Experience
Management / Oversight
Community Involvement
Change Management
QUESTIONS ?