Contaminated Sediment Sites –

The Evolution of In-Situ Capping

as an Effective Remedial Technology

IX International Seminar on

Remediation and Redevelopment of

Contaminated Sites

2 October 2014

Overview

• Sediment Remediation Utilizing Capping

• Types of Capping Technologies

• Recent Advancements in Capping Technology

• Cap Placement Delivery Systems

Introduction

The USEPA generally recognizes three major approaches

for sediment remediation:

• Monitored Natural Recovery (MNR)

• In-situ Capping

• Dredging, with Treatment and/or Disposal

The preferred remedy at large complex sites is often a

combination of alternatives as each approach has its

limitations. In-situ treatments have the potential for

increased effectiveness and significantly reduced costs over

conventional approaches.

Why are We Interested

in “In Situ” Capping?

• Recent advancements in

capping technology

• Immediate risk reduction

• Can be less expensive

than dredging

• Minimal resuspension of

contaminated sediment

• Can take less time to

implement than other

remedies

Courtesylok®

Armor Layer

Active or Passive Cap Layer

Contaminated Sediments

Benthic Layer

2000 – Present Active Caps

Example Sites:

2002 - AC, Olympic View Resource Area, WA

2003 - Coke in RCM, Apatite, Anacostia River

2006 - AC in RCM, St. Louis River, Duluth, MN

2011 – OC, Roxana Marsh, Grand Calumet, IN

2012 – AC (bulk placement), Onondaga Lake, NY

2013 – SediMiteTM (bulk placement), Mirror Lake, Dover, DE

Late 1990s Barrier Caps

Example Sites:

1999 – Clay based composite, Ottawa River, OH

1999 – Geosynthetic clay liner Little Elk Creek, MD

Late 1970s Sand / Silt and Reuse of Navigation Dredge Material

Example Site:

1978 – Sand, Stamford-New Haven, CT

In Situ Capping Innovations

Key:

AC = Activated Carbon

OC = Oleophilic Clay

RCM = Reactive Core Mat

Selection Considerations for

In Situ Capping

In Situ Capping

• Site Conditions

• Remediation Goals

• Long-Term Effectiveness

• Implementability

• Cost Effectiveness

• Sustainability

• Physical Environment

• Low Energy Environment

• Erosion Potential

• Hydrodynamic and Geotechnical Conditions

• Gas Ebullition

• Thickness of Cap

• Present and Future Use

• Source Control

Site Evaluation

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Contaminant Transport Mechanisms

Between Contaminated Sediment and Cap

• Flux – advection (groundwater upwelling)

• Flux – diffusion (concentration gradient)

• Bioturbation

• Gas Ebullition

Gas Ebullition

Cap Design

Sequence

Determine if Capping

is Appropriate for Site

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Cap Design

Sequence

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• Cap Material

• Bioturbation Component

• Consolidation Component

• Erosion Component

• Operational Component

(Cap Integrity)

• Chemical Isolation

Advantages

− Often more cost effective than removal

− Immediately reduces exposure to contaminants

− Significantly lower resuspension during implementation

− Can be shorter construction duration

Limitations

− Does not remove contamination

− Generally requires long-term monitoring and maintenance

− Often more difficult to get regulatory approval

Sediment Capping

Comparison to Dredging

Summary of Sediment

Capping Technologies

Sediment Capping

Technologies

• Conventional Capping

– Clean Sand / Sediment

• Active Capping (contaminant)

– Carbon (organics, mercury)

– Oleophilic Clay (NAPL, oils)

– Apatite / Zeolite (metals)

– Zero-Valent Iron

– Microbial Activity Enhancement

• Low cost in-situ

remediation option

• Physical isolation

• Critical factor – cap

installation

• Reduce contaminants

transfer rate

• Immobilization of

contaminant - small

Conventional Sand Cap

Contaminated

Sediment

Sand Cap

Overlying Water

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Cap Amendment Delivery Systems

Permeable Active Layer

AquaGate+PAC®

• Composite aggregate,

delivery of carbon (and other

active materials)

• Chemically sorptive

permeable layer

• Can be applied using

clamshell, broadcasting, or

conveyer

Contaminated

Sediment

SediMiteTM

Granule Layer Placement

Overlying Water

Contaminated

Sediment

Granule Breakdown

Intermixing / Bioturbation

Overlying Water Courtesy of AquaBlok®

SediMiteTM

• Minimal destruction of the existing habitat

• Mixes into the benthic layer through natural

sediment mixing processes

• Generally applied using broadcasting

• Composite aggregate barrier technology

• AquaBlok® material swells up when hydrated

• Impermeable chemically sorptive barrier

Cap Amendment Delivery Systems

AquaBlok® Cap

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Cap Amendment Delivery Systems

Reactive Core Mat® (RCM)

Supplier:

• Commercially available

• Permeable reactive cap

• Incorporate variety of media to target

specific contaminants

• Reduction in contaminant transport

• Reduced cap thickness

Courtesy of InterGEO Services

Innovative Capping Techniques

Three innovative in-situ capping technologies

developed (and utilized by);

• Sevenson Environmental Services, Inc., 2749

Lockport Road Niagara Falls, NY 14305 USA

• J.F. Brennan Co., Inc., 820 Bainbridge Street,

LaCrosse, WI 54603 USA

• Great Lakes Dock and Dredge Corporation,

2122 York Road, Oakbrook, IL 60523 USA

Water Based – BCS™

• Minimal Mixing

– Less than 1”

• Undisturbed Soft

Sediment

– Reduced velocity

placement

• Increase Accuracy

• Save Significant

Volume of Cap

Material

Capping Results

Obrigado!

George L. Hicks

Global Practice Director

Sediment Management & Remediation

CH2M HILL

Chicago, Illinois, USA