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

RemediationRisk, Inventory

Restoration

Habitat, Water Quality

NavigationDepth, Width

Some Important References

http://www.epa.gov/superfund/health/conmedia/sediment/guidance.htm

http://el.erdc.usace.army.mil/elpubs/pdf/trel08-4.pdf

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

Water Column Solids Transport

Bed Load Transport

Biologically Active Zone

Bioavailable Zone

Erosion / Deposition,

Biological Uptake

Buried Contaminated Sediments

Porewater flux,

Contaminant

degradation

Native Geologic Materials Groundwater

discharge

ZONESOME CONTAMINANT

TRANSPORT PROCESSES

SEDIMENT TRANSPORT

Sediment StabilitySome 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

GOOD PREDICTIVE MODEL

COMMON SENSE

STAKEHOLDER INPUT

DREDGING

DREDGING:

Feasibility & Design

Considerations & Terminology

Resuspension

Residuals

Dredged Material

Management

Productivity

Dredge Prism

Debris / Utilities / Structures

Dredging Technology

Delivery Techniques

Navigation

Slope Stability

Productivity

Contracting Approach

Dredging Advantages/Limitations

(per USEPA Guidance)

* Where cleanup levels achieved

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

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

Equipment Selection

Operator Experience

Best Management Practices (BMPs)

Containment (Curtains, Barriers, Sheetpile)

Innovative Approaches

Source: Bean Environmental, Cable Arm

Dredging Equipment SelectionHorizontal Profiler

Horizontal Auger (MudCat)

Cutterhead

CableArm

Some Best Management Practices for

Resuspension

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 TrendsR

ES

US

PE

NS

ION

DREDGE PRODUCTION

MASS

RATE

FRACTION OF

MASS REMOVED

NORMAL OPERATING RANGE

Navigation Sources of Resuspension

Photo provided by PANYNJ.

Contaminated Sediments

“Clean” Over-cut Sediments

Residual Sediments

Dredge

Pre-dredging

Elevation

Of River Bottom

Overdredge Depth

Design Cut Line

Sampling of

Residuals

DREDGING RESIDUALS

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

Dredging Scow Transport Hydraulic Offloading

Off-site Disposal or

Beneficial Use

http://www.foxrivercleanup.com/foxrivercleanup/photo+gallery/default.asp

http://www.dfo-mpo.gc.ca/regions/central/pub/fact-fait-mb/mb1_e.htm

Courtesy of John Henningson; Henningson Environmental Services, Inc.

Putting it All Together

http://www.foxrivercleanup.com/foxrivercleanup/photo+gallery/default.asp

Water Treatment Plant

Stockpile for Treatment /

DisposalDewatering

CAPPING

Capping Feasibility & Design

Considerations & Terminology

Thickness

Grain Size

Filter Design

Maintenance

Borrow Source Identification

Reactive Layers

Physical Barriers

Performance criteria

Pre-dredging

Habitat Layers

Cap Stability - Erosion

Cap Structure

Navigation

Porewater Fluxes

Flooding Impacts

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

Avoids risks associated with material

treatment or disposal

Usually lower cost and less disruption

than dredging and sediment

treatment/disposal

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

Cap materials may alter biological

community

Long-term monitoring and

maintenance

Placement Techniques

Hydraulic Diffuser

Conveyor

Split-Hull BargeClamshell

Source: Bean Environmental

Cap Placement Equipment - Spreader

Examples of Completed Capping

Projects (Year Completed)

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

Processing Facility Siting

Contractor Selection

Operator Experience

Management / Oversight

Community Involvement

Change Management

QUESTIONS ?